Managing real-time handwriting recognition

ABSTRACT

Methods, systems, and computer-readable media related to a technique for providing handwriting input functionality on a user device. A handwriting recognition module is trained to have a repertoire comprising multiple non-overlapping scripts and capable of recognizing tens of thousands of characters using a single handwriting recognition model. The handwriting input module provides real-time, stroke-order and stroke-direction independent handwriting recognition for multi-character handwriting input. In particular, real-time, stroke-order and stroke-direction independent handwriting recognition is provided for multi-character, or sentence level Chinese handwriting recognition. User interfaces for providing the handwriting input functionality are also disclosed.

RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/832,908, filed Jun. 9, 2013, which is incorporated by referenceherein in its entirety.

FIELD OF THE INVENTION

This specification relates to providing handwriting input functionalityon a computing device, and more specifically, to providing real-time,multi-script, stroke-order independent handwriting recognition and inputfunctionality on a computing device.

BACKGROUND

A handwriting input method is an important alternative input method forcomputing devices that are equipped with touch-sensitive surfaces (e.g.,touch-sensitive display screens, or touch-pads). Many users,particularly users in some Asian or Arab countries, are accustomed towriting in a cursive style, and may feel comfortable writing in longhandas opposed to typing on a keyboard.

For certain logographic writing systems, such as Hanzi and Kanji (alsoreferred to as Chinese characters), even though alternative syllabicinput methods (e.g., Pinyin or Kana) are available to enter charactersof the corresponding logographic writing systems, such syllabic inputmethods are inadequate when the user does not know how to phoneticallyspell a logographic character, and uses an incorrect phonetic spellingof the logographic character. Therefore, being able to use handwritinginput on a computing device becomes crucial for users who are not ableto pronounce words well enough or at all for a relevant logographicwriting system.

Although handwriting input functionality has gained some popularity incertain regions of the world, improvements are still needed. Inparticular, human handwriting is highly variable (e.g., in terms ofstroke order, size, writing style, etc.), and high-quality handwritingrecognition software is complex and requires extensive training. Assuch, providing efficient, real-time handwriting recognition on a mobiledevice having limited memory and computing resources has been achallenge.

Furthermore, in today's multi-cultural world, users in many countriesare multi-lingual, and may frequently need to write in more than onescript (e.g., writing a message in Chinese that mentions a movie titlein English). However, manually switching a recognition system to adesired script or language during writing is cumbersome and inefficient.Furthermore, the utility of conventional multi-script handwritingrecognition techniques is severely limited because scaling-up therecognition capability of a device to simultaneously handle multiplescripts vastly increases the complexity of the recognition system andthe demand on computer resources.

In addition, conventional handwriting techniques rely heavily onlanguage or script-specific particularities to achieve recognitionaccuracy. Such particularities are not easily portable to otherlanguages or scripts. Thus, adding handwriting input capabilities fornew languages or scripts is a daunting task that is not lightlyundertaken by suppliers of the software and devices. As a result, usersof many languages are deprived of an important alternative input methodfor their electronic devices.

Conventional user interfaces for providing handwriting input include anarea for accepting handwriting input from the user and an area fordisplaying handwriting recognition results. On portable devices having asmall form factor, significant improvement of the user interface isstill required to improve the efficiency, accuracy, and user experiencein general.

SUMMARY

This specification describes a technique for providing multi-scripthandwriting recognition using a universal recognizer. The universalrecognizer is trained using a large multi-script corpus of writingsamples for characters in different languages and scripts. The trainingof the universal recognizer is language-independent, script-independent,stroke-order independent, and stroke-direction independent. Thus, thesame recognizer is capable of recognizing mixed-language, mixed-scripthandwriting input without requiring manual switching between inputlanguages during use. In addition, the universal recognizer islightweight enough to be deployed as a standalone module on mobiledevices to enable handwriting input in different languages and scriptsused in different regions worldwide.

In addition, because the universal recognizer is trained onspatially-derived features which are stroke-order independent andstroke-direction independent, and require no temporal or sequenceinformation at the stroke-level, the universal recognizer providesnumerous additional features and advantages over conventionaltemporally-based recognition methods (e.g., recognition methods based onthe Hidden Markov Method (HMM)). For example, the user is permitted toenter the strokes of one or more characters, phrases, and sentences inany order, and still obtain the same recognition results. Thus,out-of-order multi-character input, and out-of-order corrections (e.g.,additions or rewrites) of earlier-entered characters are now possible.

Furthermore, the universal recognizer is used for real-time handwritingrecognition, where temporal information for each stroke is available andis optionally used to disambiguate or segment the handwriting inputbefore character recognition is performed by the universal recognizer.The real-time, stroke-order independent recognition described hereindiffers from conventional offline recognition methods (e.g., OpticalCharacter Recognition (OCR)) and can offer better performance thanconventional offline recognition methods. In addition, the universalrecognizer described herein is able to handle high variability inindividual writing habits (e.g., variability in speed, tempo,stroke-order, stroke-direction, stroke-continuity, etc.) withoutexplicitly embedding distinguishing features of the different variations(e.g., variations in speed, tempo, stroke-order, stroke-direction,stroke-continuity, etc.) in the recognition system, thereby reducing theoverall complexity of the recognition system.

As described herein, in some embodiments, temporally-derived strokedistribution information is optionally reintroduced into the universalrecognizer to enhance recognition accuracy and disambiguate betweensimilar-looking recognition outputs for the same input image. There-introduction of the temporally-derived stroke distributioninformation does not destroy the stroke-order and stroke-directionindependence of the universal recognizer, because the temporally-derivedfeatures and the spatially-derived features are obtained through aseparate training process and are only combined in the handwritingrecognition model after the separate training has been completed.Furthermore, the temporally-derived stroke distribution information iscarefully designed such that it captures distinguishing temporalcharacteristics of similar-looking characters, without relying onexplicit knowledge on the differences in the stroke-orders of thesimilar-looking characters.

User interfaces for providing handwriting input functionality are alsodescribed herein.

In some embodiments, a method of providing multi-script handwritingrecognition includes: training a multi-script handwriting recognitionmodel based on spatially-derived features of a multi-script trainingcorpus, the multi-script training corpus including respectivehandwriting samples corresponding to characters of at least threenon-overlapping scripts; and providing real-time handwriting recognitionfor a user's handwriting input using the multi-script handwritingrecognition model that has been trained on the spatially-derivedfeatures of the multi-script training corpus.

In some embodiments, a method of providing multi-script handwritingrecognition includes: receiving a multi-script handwriting recognitionmodel, the multi-script recognition model having been trained onspatially-derived features of a multi-script training corpus, themulti-script training corpus including respective handwriting samplescorresponding to characters of at least three non-overlapping scripts;receiving a handwriting input from a user, the handwriting inputcomprising one or more handwritten strokes provided on a touch-sensitivesurface coupled to the user device; and in response to receiving thehandwriting input, providing in real-time one or more handwritingrecognition results to the user based on the multi-script handwritingrecognition model that has been trained on the spatially-derivedfeatures of the multi-script training corpus.

In some embodiments, a method of providing real-time handwritingrecognition includes: receiving a plurality of handwritten strokes froma user, the plurality of handwritten strokes corresponding to ahandwritten character; generating an input image based on the pluralityof handwritten strokes; providing the input image to a handwritingrecognition model to perform real-time recognition of the handwrittencharacter, wherein the handwriting recognition model providesstroke-order independent handwriting recognition; and displaying inreal-time of receiving the plurality of handwritten strokes, anidentical first output character irrespective of a respective order bywhich the plurality of handwritten strokes have been received from theuser.

In some embodiments, the method further includes: receiving a secondplurality of handwritten strokes from the user, the second plurality ofhandwritten strokes corresponding to a second handwritten character;generating a second input image based on the second plurality ofhandwritten strokes; providing the second input image to the handwritingrecognition model to perform real-time recognition of the secondhandwritten character; and displaying in real-time of receiving thesecond plurality of handwritten strokes, a second output charactercorresponding to the second plurality of handwritten strokes, whereinthe first output character and the second output character areconcurrently displayed in a spatial sequence independent of a respectiveorder by which the first plurality of handwriting inputs and the secondplurality of handwriting inputs have been provided by the user.

In some embodiments, the second plurality of handwritten strokesspatially follow the first plurality of handwritten strokes along adefault writing direction of a handwriting input interface of the userdevice, and the second output character follows the first outputcharacter in a spatial sequence along the default writing direction, andthe method further includes: receiving a third handwritten stroke fromthe user to revise the handwritten character, the third handwrittenstroke being received temporally after the first and the secondplurality of handwritten strokes; in response to receiving the thirdhandwritten stroke, assigning the handwritten stroke to a samerecognition unit as the first plurality of handwritten strokes based onrelative proximity of the third handwritten stroke to the firstplurality of handwritten strokes; generating a revised input image basedon the first plurality of handwritten stroke and the third handwrittenstroke; providing the revised input image to the handwriting recognitionmodel to perform real-time recognition of the revised handwrittencharacter; and displaying in response to receiving the third handwritinginput, a third output character corresponding to the revised inputimage, wherein the third output character replaces the first outputcharacter and is concurrently displayed with the second output characterin the spatial sequence along the default writing direction.

In some embodiments, the method further includes: while the third outputcharacter and the second output character are concurrently displayed asa recognition result in a candidate display area of the handwritinginput interface, receiving a deletion input from the user; and inresponse to the deletion input, deleting the second output characterfrom the recognition result, while maintaining the third outputcharacter in the recognition result.

In some embodiments, rendering in real-time the first plurality ofhandwritten strokes, the second plurality of handwritten strokes, andthe third handwritten stroke in the handwriting input area of thehandwriting input interface as each of said handwritten stroke isprovided by the user; and in response to receiving the deletion input,deleting a respective rendering of the second plurality of handwrittenstrokes from the handwriting input area, while maintaining respectiverenderings of the first plurality of handwritten strokes and the thirdhandwritten stroke in the handwriting input area.

In some embodiments, a method of providing real-time handwritingrecognition includes: receiving a handwriting input from a user, thehandwriting input comprising one or more handwritten strokes provided ina handwriting input area of a handwriting input interface; based on ahandwriting recognition model, identifying a plurality of outputcharacters for the handwriting input; dividing the plurality of outputcharacters into two or more categories based on a predeterminedcategorization criterion; displaying, in an initial view of a candidatedisplay area of the handwriting input interface, respective outputcharacters in a first category of the two or more categories, whereinthe initial view of the candidate display area is concurrently providedwith an affordance for invoking an extended view of the candidatedisplay area; receiving a user input selecting the affordance forinvoking the extended view; and in response to the user input,displaying, in the extended view of the candidate display area, therespective output characters in the first category and respective outputcharacters in at least a second category of the two or more categorieswhich were not previously displayed in the initial view of the candidatedisplay area.

In some embodiments, a method of providing real-time handwritingrecognition includes: receiving a handwriting input from a user, thehandwriting input comprising a plurality of handwritten strokes providedin an handwriting input area of a handwriting input interface;recognizing, based on a handwriting recognition model, a plurality ofoutput characters from the handwriting input, the output charactersincluding at least a first emoji character and at least a firstcharacter from a script of a natural human language; and displaying arecognition result comprising the first emoji character and the firstcharacter from the script of the natural human language in a candidatedisplay area of the handwriting input interface.

In some embodiments, a method of providing handwriting recognitionincludes: receiving a handwriting input from a user, the handwritinginput comprising a plurality of handwritten strokes provided in atouch-sensitive surface coupled to the device; rendering, in real-time,the plurality of handwritten strokes in a handwriting input area of ahandwriting input interface; receiving one of a pinch gesture input anda expand gesture input over the plurality of handwritten strokes; uponreceiving a pinch gesture input, generating a first recognition resultbased on the plurality of handwritten strokes by treating the pluralityof handwritten strokes as a single recognition unit; upon receiving aexpand gesture input, generating a second recognition result based onthe plurality of handwritten strokes by treating the plurality ofhandwritten strokes as two separate recognition units pulled apart bythe expand gesture input; and upon generating a respective one of thefirst and second recognition results, displaying the generatedrecognition result in a candidate display area of the handwriting inputinterface.

In some embodiments, a method of providing handwriting recognition,includes: receiving a handwriting input from a user, the handwritinginput comprising a plurality of handwritten strokes provided in anhandwriting input area of a handwriting input interface; identifying aplurality of recognition units from the plurality of handwrittenstrokes, each recognition unit including a respective subset of theplurality of handwriting strokes; generating a multi-characterrecognition result comprising respective characters recognized from theplurality of recognition units; displaying the multi-characterrecognition result in a candidate display area of the handwriting inputinterface; while the multi-character recognition result is displayed inthe candidate display area, receiving a deletion input from the user;and in response to receiving the deletion input, removing an endcharacter from the multi-character recognition result displayed in thecandidate display area.

In some embodiments, a method of providing real-time handwritingrecognition includes: determining an orientation of the device;providing a handwriting input interface on the device in a horizontalinput mode in accordance with the device being in a first orientation,wherein a respective line of handwriting input entered in the horizontalinput mode is segmented into one or more respective recognition unitsalong a horizontal writing direction; and providing the handwritinginput interface on the device in a vertical input mode in accordancewith the device in a second orientation, wherein a respective line ofhandwriting input entered in the vertical input mode is segmented intoone or more respective recognition units along a vertical writingdirection.

In some embodiments, a method of providing real-time handwritingrecognition includes: receiving a handwriting input from a user, thehandwriting input comprising a plurality of handwritten strokes providedon a touch-sensitive surface coupled to the device; rendering theplurality of handwritten strokes in a handwriting input area of ahandwriting input interface; segmenting the plurality of handwrittenstrokes into two or more recognition units, each recognition unitcomprising a respective subset of the plurality of handwritten strokes;receiving an edit request from the user; in response to the editrequest, visually distinguishing the two or more recognition units inthe handwriting input area; and providing a means for individuallydeleting each of the two or more recognition units from the handwritinginput area.

In some embodiments, a method of providing real-time handwritingrecognition includes: receiving a first handwriting input from a user,the first handwriting input comprising a plurality of handwrittenstrokes, and the plurality of handwritten strokes forming multiplerecognition units distributed along a respective writing directionassociated with a handwriting input area of a handwriting inputinterface; rendering each of the plurality of handwritten strokes in thehandwriting input area as the handwritten stroke is provided by theuser; starting a respective fading process for each of the multiplerecognition units after the recognition unit is completely rendered,wherein during the respective fading process, the rendering of therecognition unit in the first handwriting input are becomes increasinglyfaded; receiving a second handwriting input from the user over a regionof the handwriting input area occupied by a faded recognition unit ofthe multiple recognition unit; and in response to receiving the secondhandwriting input: rendering the second handwriting input in thehandwriting input area; and clearing all faded recognition units fromthe handwriting input area.

In some embodiments, a method of providing hand-writing recognitionincludes: separately training a set of spatially-derived features and aset of temporally-derived features of a handwriting recognition model,wherein: the set of spatially-derived features are trained on a corpusof training images each being an image of a handwriting sample for arespective character of an output character set, and the set oftemporally-derived features are trained on a corpus ofstroke-distribution profiles, each stroke-distribution profilenumerically characterizing a spatial distribution of a plurality ofstrokes in a handwriting sample for a respective character of the outputcharacter set; and combining the set of spatially-derived features andthe set of temporally-derived features in the handwriting recognitionmodel; and providing real-time handwriting recognition for a user'shandwriting input using the handwriting recognition model.

The details of one or more embodiments of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages of thesubject matter will become apparent from the description, the drawings,and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a portable multifunction devicewith a touch-sensitive display in accordance with some embodiments.

FIG. 2 illustrates a portable multifunction device having atouch-sensitive display in accordance with some embodiments.

FIG. 3 is a block diagram of an exemplary multifunction device with adisplay and a touch-sensitive surface in accordance with someembodiments.

FIG. 4 illustrates an exemplary user interface for a multifunctiondevice with a touch-sensitive surface that is separate from the displayin accordance with some embodiments.

FIG. 5 is a block diagram of an operating environment of a handwritinginput system in accordance with some embodiments.

FIG. 6 is a block diagram of a multi-script handwriting recognitionmodel in accordance with some embodiments.

FIG. 7 is a flow chart of an exemplary process for training amulti-script handwriting recognition model in accordance with someembodiments.

FIGS. 8A-8B show exemplary user interfaces showing real-time,multi-script handwriting recognition and input on a portablemultifunction device in accordance with some embodiments.

FIGS. 9A-9B are flow charts of an exemplary process for providingreal-time multi-script handwriting recognition and input on a portablemultifunction device.

FIGS. 10A-10C are flow charts of an exemplary process for providingreal-time stroke-order independent handwriting recognition and input ona portable multifunction device in accordance with some embodiments.

FIGS. 11A-11K show exemplary user interfaces for selectively displayingone category of recognition results in a normal view of a candidatedisplay area, and other categories of recognition results in an extendedview of the candidate display area, in accordance with some embodiments.

FIGS. 12A-12B is are flow charts of an exemplary process for selectivelydisplaying one category of recognition results in a normal view of acandidate display area, and other categories of recognition results inan extended view of the candidate display area, in accordance with someembodiments.

FIGS. 13A-13E show exemplary user interfaces for entering emojicharacters through handwriting input in accordance with someembodiments.

FIG. 14 is a flow chart of an exemplary process for entering emojicharacters through handwriting input in accordance with someembodiments.

FIGS. 15A-15K show exemplary user interfaces for using a pinch or expandgesture to inform the handwriting input module about how to divide acurrently accumulated handwriting input into one or more recognitionunits, in accordance with some embodiments.

FIGS. 16A-16B are flow charts of an exemplary process for using a pinchor expand gesture to inform the handwriting input module about how todivide a currently accumulated handwriting input into one or morerecognition units, in accordance with some embodiments.

FIGS. 17A-17H show exemplary user interfaces for providingcharacter-by-character deletion of a user's handwriting input inaccordance with some embodiments.

FIGS. 18A-18B are flow charts of an exemplary process for providingcharacter-by-character deletion of a user's handwriting input inaccordance with some embodiments.

FIGS. 19A-19F show exemplary user interfaces for switching between avertical writing mode and a horizontal writing mode in accordance withsome embodiments.

FIGS. 20A-20C are flow charts of an exemplary process for switchingbetween a vertical writing mode and a horizontal writing mode inaccordance with some embodiments.

FIGS. 21A-21H show user interfaces for providing a means to display andselectively delete individual recognition units identified in a user'shandwriting input, in accordance with some embodiments.

FIGS. 22A-22B are flow charts of an exemplary process for providing ameans to display and selectively delete individual recognition unitsidentified in a user's handwriting input, in accordance with someembodiments.

FIGS. 23A-23L show exemplary user interfaces for utilizing a newhandwriting input provided over an existing handwriting input in thehandwriting input area as an implicit confirmation input for entering arecognition result displayed for the existing handwriting input, inaccordance with some embodiments.

FIGS. 24A-24B are flow charts of an exemplary process for utilizing anew handwriting input provided over an existing handwriting input in thehandwriting input area as an implicit confirmation input for entering arecognition result displayed for the existing handwriting input, inaccordance with some embodiments.

FIGS. 25A-25B are flow charts of an exemplary process for integratingtemporally-derived stroked distribution information into a handwritingrecognition model based on spatially-derived features, withoutdestroying the stroke-order and stroke direction independence of thehandwriting recognition model, in accordance with some embodiments.

FIG. 26 is a block diagram illustrating separate training and subsequentintegration of spatially-derived features and temporally-derivedfeatures of an exemplary handwriting recognition system in accordancewith some embodiments.

FIG. 27 is a block diagram illustrating an exemplary method forcomputing the stroke distribution profile of a character.

Like reference numerals refer to corresponding parts throughout thedrawings.

DETAILED DESCRIPTION

Many electronic devices have graphical user interfaces with softkeyboards for character entry. On some electronic devices, a user mayalso be able to install or enable a handwriting input interface thatallows the user to input characters via handwriting on a touch-sensitivedisplay screen or a touch-sensitive surface coupled to the devices.Conventional handwriting recognition input methods and user interfaceshave a number of issues and shortcomings. For example,

-   -   In general, conventional handwriting input functionality is        enabled language-by-language or script-by-script. Each        additional input language requires installation of a separate        handwriting recognition model that takes-up separate storage        space and memory. Little synergy is provided by combining the        handwriting recognition models for different languages, and        mixed-language or mixed-script handwriting recognition        conventionally took a very long time due to a complex        disambiguation process.    -   In addition, because conventional handwriting recognition        systems rely heavily on language-specific or script-specific        characteristics for character recognition. Recognition of mixed        language handwriting input had a poor accuracy. Furthermore,        available combinations of recognized languages are very limited.        Most systems required the user to manually specify the desired        language-specific handwriting recognizer before providing        handwriting input in each non-default language or script.    -   Many existing real-time handwriting recognition models require        temporal or sequence information on a stroke-by-stroke level,        which produce inaccurate recognition results when dealing with        the high variability of how a character can be written (e.g.,        high variability in the shape, length, tempo, segmentation,        order, and direction of strokes due to writing styles and        personal habits). Some systems also require users to adhere to        strict spatial and temporal criteria (e.g., with built-in        assumptions on the size, sequence, and timeframe of each        character input) when providing a handwriting input. Any        deviation from these criteria caused inaccurate recognition        results that were difficult to correct.    -   Currently, most real-time handwriting input interfaces only        allow the user to enter a few characters at a time. Entry of        long phrases or sentences are broken down into short segments        and inputted separately. This stilted input not only places        cognitive burden on the user to maintain the flow of the        composition, but also makes it difficult for the user to correct        or revise an earlier entered character or phrase.

The embodiments described below address these and related issues.

FIGS. 1-4 below, provide a description of exemplary devices. FIGS. 5, 6,and 26-27 illustrate exemplary handwriting recognition and inputsystems. FIGS. 8A-8B, 11A-11K, 13A-13E, 15A-15K, 17A-17H, 19A-19F,21A-21H, 23A-12L illustrate exemplary user interfaces for handwritingrecognition and input. FIGS. 7, 9A-9B, 10A-10C, 12A-12B, 14, 16A-16B,18A-18B, 20A-20C, 22A-22B, 24A-24B, and 25 are flow charts illustratingmethods of enabling handwriting recognition and input on user devices,including training handwriting recognition models, providing real-timehandwriting recognition results, providing means for inputting andrevising a handwriting input, and providing means for entering arecognition result as a text input. The user interfaces in FIGS. 8A-8B,11A-11K, 13A-13E, 15A-15K, 17A-17H, 19A-19F, 21A-21H, 23A-12L are usedto illustrate the processes in FIGS. 7, 9A-9B, 10A-10C, 12A-12B, 14,16A-16B, 18A-18B, 20A-20C, 22A-22B, 24A-24B, and 25.

Exemplary Devices

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings. In the following detaileddescription, numerous specific details are set forth in order to providea thorough understanding of the present invention. However, it will beapparent to one of ordinary skill in the art that the present inventionmay be practiced without these specific details. In other instances,well-known methods, procedures, components, circuits, and networks havenot been described in detail so as not to unnecessarily obscure aspectsof the embodiments.

It will also be understood that, although the terms first, second, etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These terms are only used to distinguishone element from another. For example, a first contact could be termed asecond contact, and, similarly, a second contact could be termed a firstcontact, without departing from the scope of the present invention. Thefirst contact and the second contact are both contacts, but they are notthe same contact.

The terminology used in the description of the invention herein is forthe purpose of describing particular embodiments only and is notintended to be limiting of the invention. As used in the description ofthe invention and the appended claims, the singular forms “a”, “an” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. It will also be understood that theterm “and/or” as used herein refers to and encompasses any and allpossible combinations of one or more of the associated listed items. Itwill be further understood that the terms “includes,” “including,”“comprises,” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

As used herein, the term “if” may be construed to mean “when” or “upon”or “in response to determining” or “in response to detecting,” dependingon the context. Similarly, the phrase “if it is determined” or “if [astated condition or event] is detected” may be construed to mean “upondetermining” or “in response to determining” or “upon detecting [thestated condition or event]” or “in response to detecting [the statedcondition or event],” depending on the context.

Embodiments of electronic devices, user interfaces for such devices, andassociated processes for using such devices are described. In someembodiments, the device is a portable communications device, such as amobile telephone, that also contains other functions, such as PDA and/ormusic player functions. Exemplary embodiments of portable multifunctiondevices include, without limitation, the iPhone®, iPod Touch®, and iPad®devices from Apple Inc. of Cupertino, Calif. Other portable electronicdevices, such as laptops or tablet computers with touch-sensitivesurfaces (e.g., touch screen displays and/or touch pads), may also beused. It should also be understood that, in some embodiments, the deviceis not a portable communications device, but is a desktop computer witha touch-sensitive surface (e.g., a touch screen display and/or a touchpad).

In the discussion that follows, an electronic device that includes adisplay and a touch-sensitive surface is described. It should beunderstood, however, that the electronic device may include one or moreother physical user-interface devices, such as a physical keyboard, amouse and/or a joystick.

The device typically supports a variety of applications, such as one ormore of the following: a drawing application, a presentationapplication, a word processing application, a website creationapplication, a disk authoring application, a spreadsheet application, agaming application, a telephone application, a video conferencingapplication, an e-mail application, an instant messaging application, aworkout support application, a photo management application, a digitalcamera application, a digital video camera application, a web browsingapplication, a digital music player application, and/or a digital videoplayer application.

The various applications that may be executed on the device may use atleast one common physical user-interface device, such as thetouch-sensitive surface. One or more functions of the touch-sensitivesurface as well as corresponding information displayed on the device maybe adjusted and/or varied from one application to the next and/or withina respective application. In this way, a common physical architecture(such as the touch-sensitive surface) of the device may support thevariety of applications with user interfaces that are intuitive andtransparent to the user.

Attention is now directed toward embodiments of portable devices withtouch-sensitive displays. FIG. 1 is a block diagram illustratingportable multifunction device 100 with touch-sensitive displays 112 inaccordance with some embodiments. Touch-sensitive display 112 issometimes called a “touch screen” for convenience, and may also be knownas or called a touch-sensitive display system. Device 100 may includememory 102 (which may include one or more computer readable storagemediums), memory controller 122, one or more processing units (CPU's)120, peripherals interface 118, RF circuitry 108, audio circuitry 110,speaker 111, microphone 113, input/output (I/O) subsystem 106, otherinput or control devices 116, and external port 124. Device 100 mayinclude one or more optical sensors 164. These components maycommunicate over one or more communication buses or signal lines 103.

It should be appreciated that device 100 is only one example of aportable multifunction device, and that device 100 may have more orfewer components than shown, may combine two or more components, or mayhave a different configuration or arrangement of the components. Thevarious components shown in FIG. 1 may be implemented in hardware,software, or a combination of both hardware and software, including oneor more signal processing and/or application specific integratedcircuits.

Memory 102 may include high-speed random access memory and may alsoinclude non-volatile memory, such as one or more magnetic disk storagedevices, flash memory devices, or other non-volatile solid-state memorydevices. Access to memory 102 by other components of device 100, such asCPU 120 and the peripherals interface 118, may be controlled by memorycontroller 122.

Peripherals interface 118 can be used to couple input and outputperipherals of the device to CPU 120 and memory 102. The one or moreprocessors 120 run or execute various software programs and/or sets ofinstructions stored in memory 102 to perform various functions fordevice 100 and to process data.

In some embodiments, peripherals interface 118, CPU 120, and memorycontroller 122 may be implemented on a single chip, such as chip 104. Insome other embodiments, they may be implemented on separate chips.

RF (radio frequency) circuitry 108 receives and sends RF signals, alsocalled electromagnetic signals. RF circuitry 108 converts electricalsignals to/from electromagnetic signals and communicates withcommunications networks and other communications devices via theelectromagnetic signals.

Audio circuitry 110, speaker 111, and microphone 113 provide an audiointerface between a user and device 100. Audio circuitry 110 receivesaudio data from peripherals interface 118, converts the audio data to anelectrical signal, and transmits the electrical signal to speaker 111.Speaker 111 converts the electrical signal to human-audible sound waves.Audio circuitry 110 also receives electrical signals converted bymicrophone 113 from sound waves. Audio circuitry 110 converts theelectrical signal to audio data and transmits the audio data toperipherals interface 118 for processing. Audio data may be retrievedfrom and/or transmitted to memory 102 and/or RF circuitry 108 byperipherals interface 118. In some embodiments, audio circuitry 110 alsoincludes a headset jack (e.g., 212, FIG. 2).

I/O subsystem 106 couples input/output peripherals on device 100, suchas touch screen 112 and other input control devices 116, to peripheralsinterface 118. I/O subsystem 106 may include display controller 156 andone or more input controllers 160 for other input or control devices.The one or more input controllers 160 receive/send electrical signalsfrom/to other input or control devices 116. The other input controldevices 116 may include physical buttons (e.g., push buttons, rockerbuttons, etc.), dials, slider switches, joysticks, click wheels, and soforth. In some alternate embodiments, input controller(s) 160 may becoupled to any (or none) of the following: a keyboard, infrared port,USB port, and a pointer device such as a mouse. The one or more buttons(e.g., 208, FIG. 2) may include an up/down button for volume control ofspeaker 111 and/or microphone 113. The one or more buttons may include apush button (e.g., 206, FIG. 2).

Touch-sensitive display 112 provides an input interface and an outputinterface between the device and a user. Display controller 156 receivesand/or sends electrical signals from/to touch screen 112. Touch screen112 displays visual output to the user. The visual output may includegraphics, text, icons, video, and any combination thereof (collectivelytermed “graphics”). In some embodiments, some or all of the visualoutput may correspond to user-interface objects.

Touch screen 112 has a touch-sensitive surface, sensor or set of sensorsthat accepts input from the user based on haptic and/or tactile contact.Touch screen 112 and display controller 156 (along with any associatedmodules and/or sets of instructions in memory 102) detect contact (andany movement or breaking of the contact) on touch screen 112 andconverts the detected contact into interaction with user-interfaceobjects (e.g., one or more soft keys, icons, web pages or images) thatare displayed on touch screen 112. In an exemplary embodiment, a pointof contact between touch screen 112 and the user corresponds to a fingerof the user.

Touch screen 112 may use LCD (liquid crystal display) technology, LPD(light emitting polymer display) technology, or LED (light emittingdiode) technology, although other display technologies may be used inother embodiments. Touch screen 112 and display controller 156 maydetect contact and any movement or breaking thereof using any of aplurality of touch sensing technologies now known or later developed,including but not limited to capacitive, resistive, infrared, andsurface acoustic wave technologies, as well as other proximity sensorarrays or other elements for determining one or more points of contactwith touch screen 112. In an exemplary embodiment, projected mutualcapacitance sensing technology is used, such as that found in theiPhone®, iPod Touch®, and iPad® from Apple Inc. of Cupertino, Calif.

Touch screen 112 may have a video resolution in excess of 100 dpi. Insome embodiments, the touch screen has a video resolution ofapproximately 160 dpi. The user may make contact with touch screen 112using any suitable object or appendage, such as a stylus, a finger, andso forth. In some embodiments, the user interface is designed to workprimarily with finger-based contacts and gestures, which can be lessprecise than stylus-based input due to the larger area of contact of afinger on the touch screen. In some embodiments, the device translatesthe rough finger-based input into a precise pointer/cursor position orcommand for performing the actions desired by the user. Handwritinginput may be provided on the touch screen 112 via locations andmovements of finger-based or stylus-based contacts. In some embodiments,the touch screen 112 renders the finger-based or stylus-based input asinstantaneous visual feedback to the current handwriting input, andprovides the visual effect of actual writing on a writing surface (e.g.,a sheet of paper) with a writing instrument (e.g., a pen).

In some embodiments, in addition to the touch screen, device 100 mayinclude a touchpad (not shown) for activating or deactivating particularfunctions. In some embodiments, the touchpad is a touch-sensitive areaof the device that, unlike the touch screen, does not display visualoutput. The touchpad may be a touch-sensitive surface that is separatefrom touch screen 112 or an extension of the touch-sensitive surfaceformed by the touch screen.

Device 100 also includes power system 162 for powering the variouscomponents. Power system 162 may include a power management system, oneor more power sources (e.g., battery, alternating current (AC)), arecharging system, a power failure detection circuit, a power converteror inverter, a power status indicator (e.g., a light-emitting diode(LED)) and any other components associated with the generation,management and distribution of power in portable devices.

Device 100 may also include one or more optical sensors 164. FIG. 1shows an optical sensor coupled to optical sensor controller 158 in I/Osubsystem 106. Optical sensor 164 may include charge-coupled device(CCD) or complementary metal-oxide semiconductor (CMOS)phototransistors. Optical sensor 164 receives light from theenvironment, projected through one or more lens, and converts the lightto data representing an image. In conjunction with imaging module 143(also called a camera module), optical sensor 164 may capture stillimages or video.

Device 100 may also include one or more proximity sensors 166. FIG. 1shows proximity sensor 166 coupled to peripherals interface 118.Alternately, proximity sensor 166 may be coupled to input controller 160in I/O subsystem 106. In some embodiments, the proximity sensor turnsoff and disables touch screen 112 when the multifunction device isplaced near the user's ear (e.g., when the user is making a phone call).

Device 100 may also include one or more accelerometers 168. FIG. 1 showsaccelerometer 168 coupled to peripherals interface 118. Alternately,accelerometer 168 may be coupled to an input controller 160 in I/Osubsystem 106. In some embodiments, information is displayed on thetouch screen display in a portrait view or a landscape view based on ananalysis of data received from the one or more accelerometers. Device100 optionally includes, in addition to accelerometer(s) 168, amagnetometer (not shown) and a GPS (or GLONASS or other globalnavigation system) receiver (not shown) for obtaining informationconcerning the location and orientation (e.g., portrait or landscape) ofdevice 100.

In some embodiments, the software components stored in memory 102include operating system 126, communication module (or set ofinstructions) 128, contact/motion module (or set of instructions) 130,graphics module (or set of instructions) 132, text input module (or setof instructions) 134, Global Positioning System (GPS) module (or set ofinstructions) 135, and applications (or sets of instructions) 136.Furthermore, in some embodiments, memory 102 stores handwriting inputmodule 157, as shown in FIGS. 1 and 3. The handwriting input module 157includes a handwriting recognition model, and provides handwritingrecognition and input function to a user of the device 100 (or device300). More details of the handwriting input module 157 are provided withrespect to FIGS. 5-27 and accompanying descriptions thereof.

Operating system 126 (e.g., Darwin, RTXC, LINUX, UNIX, OS X, WINDOWS, oran embedded operating system such as VxWorks) includes various softwarecomponents and/or drivers for controlling and managing general systemtasks (e.g., memory management, storage device control, powermanagement, etc.) and facilitates communication between various hardwareand software components.

Communication module 128 facilitates communication with other devicesover one or more external ports 124 and also includes various softwarecomponents for handling data received by RF circuitry 108 and/orexternal port 124. External port 124 (e.g., Universal Serial Bus (USB),FIREWIRE, etc.) is adapted for coupling directly to other devices orindirectly over a network (e.g., the Internet, wireless LAN, etc.).

Contact/motion module 130 may detect contact with touch screen 112 (inconjunction with display controller 156) and other touch sensitivedevices (e.g., a touchpad or physical click wheel). Contact/motionmodule 130 includes various software components for performing variousoperations related to detection of contact, such as determining ifcontact has occurred (e.g., detecting a finger-down event), determiningif there is movement of the contact and tracking the movement across thetouch-sensitive surface (e.g., detecting one or more finger-draggingevents), and determining if the contact has ceased (e.g., detecting afinger-up event or a break in contact). Contact/motion module 130receives contact data from the touch-sensitive surface. Determiningmovement of the point of contact, which is represented by a series ofcontact data, may include determining speed (magnitude), velocity(magnitude and direction), and/or an acceleration (a change in magnitudeand/or direction) of the point of contact. These operations may beapplied to single contacts (e.g., one finger contacts) or to multiplesimultaneous contacts (e.g., “multitouch”/multiple finger contacts). Insome embodiments, contact/motion module 130 and display controller 156detect contact on a touchpad.

Contact/motion module 130 may detect a gesture input by a user.Different gestures on the touch-sensitive surface have different contactpatterns. Thus, a gesture may be detected by detecting a particularcontact pattern. For example, detecting a finger tap gesture includesdetecting a finger-down event followed by detecting a finger-up (liftoff) event at the same position (or substantially the same position) asthe finger-down event (e.g., at the position of an icon). As anotherexample, detecting a finger swipe gesture on the touch-sensitive surfaceincludes detecting a finger-down event followed by detecting one or morefinger-dragging events, and subsequently followed by detecting afinger-up (lift off) event.

Contact/motion module 130 is optionally utilized by the handwritinginput module 157 to register input of handwritten strokes within ahandwriting input area of a handwriting input interface displayed on thetouch-sensitive display screen 112 (or within an area of the touch-pad355 corresponding to the handwriting input area displayed on display 340in FIG. 3). In some embodiments, locations, motion path, and intensitiesassociated with the contact during the initial finger-down event, thefinal finger-up event, any time there between is recorded as ahandwritten stroke. Based on such information, the handwritten strokescan be rendered on the display, as feedback for the user input. Inaddition, one or more input images can be generated based on handwrittenstrokes registered by the contact/motion module 130.

Graphics module 132 includes various known software components forrendering and displaying graphics on touch screen 112 or other display,including components for changing the intensity of graphics that aredisplayed. As used herein, the term “graphics” includes any object thatcan be displayed to a user, including without limitation text, webpages, icons (such as user-interface objects including soft keys),digital images, videos, animations and the like.

In some embodiments, graphics module 132 stores data representinggraphics to be used. Each graphic may be assigned a corresponding code.Graphics module 132 receives, from applications etc., one or more codesspecifying graphics to be displayed along with, if necessary, coordinatedata and other graphic property data, and then generates screen imagedata to output to display controller 156.

Text input module 134, which may be a component of graphics module 132,provides soft keyboards for entering text in various applications (e.g.,contacts 137, e-mail 140, IM 141, browser 147, and any other applicationthat needs text input). In some embodiments, the handwriting inputmodule 157 is optionally invocated through a user interface of the textinput module 134, e.g., though a keyboard selection affordance. In someembodiments, the same or similar keyboard selection affordance is alsoprovided in the handwriting input interface to invoke the text inputmodule 134.

GPS module 135 determines the location of the device and provides thisinformation for use in various applications (e.g., to telephone 138 foruse in location-based dialing, to camera 143 as picture/video metadata,and to applications that provide location-based services such as weatherwidgets, local yellow page widgets, and map/navigation widgets).

Applications 136 may include the following modules (or sets ofinstructions), or a subset or superset thereof: contacts module 137(sometimes called an address book or contact list); telephone module138; video conferencing module 139; e-mail client module 140; instantmessaging (IM) module 141; workout support module 142; camera module 143for still and/or video images; image management module 144; browsermodule 147; calendar module 148; widget modules 149, which may includeone or more of: weather widget 149-1, stocks widget 149-2, calculatorwidget 149-3, alarm clock widget 149-4, dictionary widget 149-5, andother widgets obtained by the user, as well as user-created widgets149-6; widget creator module 150 for making user-created widgets 149-6;search module 151; video and music player module 152, which may be madeup of a video player module and a music player module; notes module 153;map module 154; and/or online video module 155.

Examples of other applications 136 that may be stored in memory 102include other word processing applications, other image editingapplications, drawing applications, presentation applications,JAVA-enabled applications, encryption, digital rights management, voicerecognition, and voice replication.

In conjunction with touch screen 112, display controller 156, contactmodule 130, graphics module 132, handwriting input module 157, and textinput module 134, contacts module 137 may be used to manage an addressbook or contact list (e.g., stored in application internal state 192 ofcontacts module 137 in memory 102 or memory 370), including: addingname(s) to the address book; deleting name(s) from the address book;associating telephone number(s), e-mail address(es), physicaladdress(es) or other information with a name; associating an image witha name; categorizing and sorting names; providing telephone numbers ore-mail addresses to initiate and/or facilitate communications bytelephone 138, video conference 139, e-mail 140, or IM 141; and soforth.

In conjunction with RF circuitry 108, audio circuitry 110, speaker 111,microphone 113, touch screen 112, display controller 156, contact module130, graphics module 132, handwriting input module 157, and text inputmodule 134, telephone module 138 may be used to enter a sequence ofcharacters corresponding to a telephone number, access one or moretelephone numbers in address book 137, modify a telephone number thathas been entered, dial a respective telephone number, conduct aconversation and disconnect or hang up when the conversation iscompleted. As noted above, the wireless communication may use any of aplurality of communications standards, protocols and technologies.

In conjunction with RF circuitry 108, audio circuitry 110, speaker 111,microphone 113, touch screen 112, display controller 156, optical sensor164, optical sensor controller 158, contact module 130, graphics module132, handwriting input module 157, text input module 134, contact list137, and telephone module 138, videoconferencing module 139 includesexecutable instructions to initiate, conduct, and terminate a videoconference between a user and one or more other participants inaccordance with user instructions.

In conjunction with RF circuitry 108, touch screen 112, displaycontroller 156, contact module 130, graphics module 132, handwritinginput module 157, and text input module 134, e-mail client module 140includes executable instructions to create, send, receive, and managee-mail in response to user instructions. In conjunction with imagemanagement module 144, e-mail client module 140 makes it very easy tocreate and send e-mails with still or video images taken with cameramodule 143.

In conjunction with RF circuitry 108, touch screen 112, displaycontroller 156, contact module 130, graphics module 132, handwritinginput module 157, and text input module 134, the instant messagingmodule 141 includes executable instructions to enter a sequence ofcharacters corresponding to an instant message, to modify previouslyentered characters, to transmit a respective instant message (forexample, using a Short Message Service (SMS) or Multimedia MessageService (MMS) protocol for telephony-based instant messages or usingXMPP, SIMPLE, or IMPS for Internet-based instant messages), to receiveinstant messages and to view received instant messages. In someembodiments, transmitted and/or received instant messages may includegraphics, photos, audio files, video files and/or other attachments asare supported in a MMS and/or an Enhanced Messaging Service (EMS). Asused herein, “instant messaging” refers to both telephony-based messages(e.g., messages sent using SMS or MMS) and Internet-based messages(e.g., messages sent using XMPP, SIMPLE, or IMPS).

In conjunction with RF circuitry 108, touch screen 112, displaycontroller 156, contact module 130, graphics module 132, handwritinginput module 157, text input module 134, GPS module 135, map module 154,and music player module 146, workout support module 142 includesexecutable instructions to create workouts (e.g., with time, distance,and/or calorie burning goals); communicate with workout sensors (sportsdevices); receive workout sensor data; calibrate sensors used to monitora workout; select and play music for a workout; and display, store andtransmit workout data.

In conjunction with touch screen 112, display controller 156, opticalsensor(s) 164, optical sensor controller 158, contact module 130,graphics module 132, and image management module 144, camera module 143includes executable instructions to capture still images or video(including a video stream) and store them into memory 102, modifycharacteristics of a still image or video, or delete a still image orvideo from memory 102.

In conjunction with touch screen 112, display controller 156, contactmodule 130, graphics module 132, handwriting input module 157, textinput module 134, and camera module 143, image management module 144includes executable instructions to arrange, modify (e.g., edit), orotherwise manipulate, label, delete, present (e.g., in a digital slideshow or album), and store still and/or video images.

In conjunction with RF circuitry 108, touch screen 112, display systemcontroller 156, contact module 130, graphics module 132, handwritinginput module 157, and text input module 134, browser module 147 includesexecutable instructions to browse the Internet in accordance with userinstructions, including searching, linking to, receiving, and displayingweb pages or portions thereof, as well as attachments and other fileslinked to web pages.

In conjunction with RF circuitry 108, touch screen 112, display systemcontroller 156, contact module 130, graphics module 132, handwritinginput module 157, text input module 134, e-mail client module 140, andbrowser module 147, calendar module 148 includes executable instructionsto create, display, modify, and store calendars and data associated withcalendars (e.g., calendar entries, to do lists, etc.) in accordance withuser instructions.

In conjunction with RF circuitry 108, touch screen 112, display systemcontroller 156, contact module 130, graphics module 132, handwritinginput module 157, text input module 134, and browser module 147, widgetmodules 149 are mini-applications that may be downloaded and used by auser (e.g., weather widget 149-1, stocks widget 149-2, calculator widget149-3, alarm clock widget 149-4, and dictionary widget 149-5) or createdby the user (e.g., user-created widget 149-6). In some embodiments, awidget includes an HTML (Hypertext Markup Language) file, a CSS(Cascading Style Sheets) file, and a JavaScript file. In someembodiments, a widget includes an XML (Extensible Markup Language) fileand a JavaScript file (e.g., Yahoo! Widgets).

In conjunction with RF circuitry 108, touch screen 112, display systemcontroller 156, contact module 130, graphics module 132, handwritinginput module 157, text input module 134, and browser module 147, thewidget creator module 150 may be used by a user to create widgets (e.g.,turning a user-specified portion of a web page into a widget).

In conjunction with touch screen 112, display system controller 156,contact module 130, graphics module 132, handwriting input module 157,and text input module 134, search module 151 includes executableinstructions to search for text, music, sound, image, video, and/orother files in memory 102 that match one or more search criteria (e.g.,one or more user-specified search terms) in accordance with userinstructions.

In conjunction with touch screen 112, display system controller 156,contact module 130, graphics module 132, audio circuitry 110, speaker111, RF circuitry 108, and browser module 147, video and music playermodule 152 includes executable instructions that allow the user todownload and play back recorded music and other sound files stored inone or more file formats, such as MP3 or AAC files, and executableinstructions to display, present or otherwise play back videos (e.g., ontouch screen 112 or on an external, connected display via external port124). In some embodiments, device 100 may include the functionality ofan MP3 player, such as an iPod (trademark of Apple Inc.).

In conjunction with touch screen 112, display controller 156, contactmodule 130, graphics module 132, handwriting input module 157, and textinput module 134, notes module 153 includes executable instructions tocreate and manage notes, to do lists, and the like in accordance withuser instructions.

In conjunction with RF circuitry 108, touch screen 112, display systemcontroller 156, contact module 130, graphics module 132, handwritinginput module 157, text input module 134, GPS module 135, and browsermodule 147, map module 154 may be used to receive, display, modify, andstore maps and data associated with maps (e.g., driving directions; dataon stores and other points of interest at or near a particular location;and other location-based data) in accordance with user instructions.

In conjunction with touch screen 112, display system controller 156,contact module 130, graphics module 132, audio circuitry 110, speaker111, RF circuitry 108, handwriting input module 157, text input module134, e-mail client module 140, and browser module 147, online videomodule 155 includes instructions that allow the user to access, browse,receive (e.g., by streaming and/or download), play back (e.g., on thetouch screen or on an external, connected display via external port124), send an e-mail with a link to a particular online video, andotherwise manage online videos in one or more file formats, such asH.264. In some embodiments, instant messaging module 141, rather thane-mail client module 140, is used to send a link to a particular onlinevideo.

Each of the above identified modules and applications correspond to aset of executable instructions for performing one or more functionsdescribed above and the methods described in this application (e.g., thecomputer-implemented methods and other information processing methodsdescribed herein). These modules (i.e., sets of instructions) need notbe implemented as separate software programs, procedures or modules, andthus various subsets of these modules may be combined or otherwisere-arranged in various embodiments. In some embodiments, memory 102 maystore a subset of the modules and data structures identified above.Furthermore, memory 102 may store additional modules and data structuresnot described above.

In some embodiments, device 100 is a device where operation of apredefined set of functions on the device is performed exclusivelythrough a touch screen and/or a touchpad. By using a touch screen and/ora touchpad as the primary input control device for operation of device100, the number of physical input control devices (such as push buttons,dials, and the like) on device 100 may be reduced.

FIG. 2 illustrates a portable multifunction device 100 having a touchscreen 112 in accordance with some embodiments. The touch screen maydisplay one or more graphics within user interface (UI) 200. In thisembodiment, as well as others described below, a user may select one ormore of the graphics by making a gesture on the graphics, for example,with one or more fingers 202 (not drawn to scale in the figure) or oneor more styluses 203 (not drawn to scale in the figure). In someembodiments, selection of one or more graphics occurs when the userbreaks contact with the one or more graphics. In some embodiments, thegesture may include one or more taps, one or more swipes (from left toright, right to left, upward and/or downward) and/or a rolling of afinger (from right to left, left to right, upward and/or downward) thathas made contact with device 100. In some embodiments, inadvertentcontact with a graphic may not select the graphic. For example, a swipegesture that sweeps over an application icon may not select thecorresponding application when the gesture corresponding to selection isa tap.

Device 100 may also include one or more physical buttons, such as “home”or menu button 204. As described previously, menu button 204 may be usedto navigate to any application 136 in a set of applications that may beexecuted on device 100. Alternatively, in some embodiments, the menubutton is implemented as a soft key in a GUI displayed on touch screen112.

In one embodiment, device 100 includes touch screen 112, menu button204, push button 206 for powering the device on/off and locking thedevice, volume adjustment button(s) 208, Subscriber Identity Module(SIM) card slot 210, head set jack 212, and docking/charging externalport 124. Push button 206 may be used to turn the power on/off on thedevice by depressing the button and holding the button in the depressedstate for a predefined time interval; to lock the device by depressingthe button and releasing the button before the predefined time intervalhas elapsed; and/or to unlock the device or initiate an unlock process.In an alternative embodiment, device 100 also may accept verbal inputfor activation or deactivation of some functions through microphone 113.

FIG. 3 is a block diagram of an exemplary multifunction device with adisplay and a touch-sensitive surface in accordance with someembodiments. Device 300 need not be portable. In some embodiments,device 300 is a laptop computer, a desktop computer, a tablet computer,a multimedia player device, a navigation device, an educational device(such as a child's learning toy), a gaming system, a telephony device,or a control device (e.g., a home or industrial controller). Device 300typically includes one or more processing units (CPU's) 310, one or morenetwork or other communications interfaces 360, memory 370, and one ormore communication buses 320 for interconnecting these components.Communication buses 320 may include circuitry (sometimes called achipset) that interconnects and controls communications between systemcomponents. Device 300 includes input/output (I/O) interface 330comprising display 340, which is typically a touch screen display. I/Ointerface 330 also may include a keyboard and/or mouse (or otherpointing device) 350 and touchpad 355. Memory 370 includes high-speedrandom access memory, such as DRAM, SRAM, DDR RAM or other random accesssolid state memory devices; and may include non-volatile memory, such asone or more magnetic disk storage devices, optical disk storage devices,flash memory devices, or other non-volatile solid state storage devices.Memory 370 may optionally include one or more storage devices remotelylocated from CPU(s) 310. In some embodiments, memory 370 storesprograms, modules, and data structures analogous to the programs,modules, and data structures stored in memory 102 of portablemultifunction device 100 (FIG. 1), or a subset thereof. Furthermore,memory 370 may store additional programs, modules, and data structuresnot present in memory 102 of portable multifunction device 100. Forexample, memory 370 of device 300 may store drawing module 380,presentation module 382, word processing module 384, website creationmodule 386, disk authoring module 388, and/or spreadsheet module 390,while memory 102 of portable multifunction device 100 (FIG. 1) may notstore these modules.

Each of the above identified elements in FIG. 3 may be stored in one ormore of the previously mentioned memory devices. Each of the aboveidentified modules corresponds to a set of instructions for performing afunction described above. The above identified modules or programs(i.e., sets of instructions) need not be implemented as separatesoftware programs, procedures or modules, and thus various subsets ofthese modules may be combined or otherwise re-arranged in variousembodiments. In some embodiments, memory 370 may store a subset of themodules and data structures identified above. Furthermore, memory 370may store additional modules and data structures not described above.

FIG. 4 illustrates an exemplary user interface on a device (e.g., device300, FIG. 3) with a touch-sensitive surface 451 (e.g., a tablet ortouchpad 355, FIG. 3) that is separate from the display 450 (e.g., touchscreen display 112). Although many of the examples which follow will begiven with reference to inputs on touch screen display 112 (where thetouch sensitive surface and the display are combined), in someembodiments, the device detects inputs on a touch-sensitive surface thatis separate from the display, as shown in FIG. 4. In some embodimentsthe touch sensitive surface (e.g., 451 in FIG. 4) has a primary axis(e.g., 452 in FIG. 4) that corresponds to a primary axis (e.g., 453 inFIG. 4) on the display (e.g., 450). In accordance with theseembodiments, the device detects contacts (e.g., 460 and 462 in FIG. 4)with the touch-sensitive surface 451 at locations that correspond torespective locations on the display (e.g., in FIG. 4, 460 corresponds to468 and 462 corresponds to 470). In this way, user inputs (e.g.,contacts 460 and 462, and movements thereof) detected by the device onthe touch-sensitive surface (e.g., 451 in FIG. 4) are used by the deviceto manipulate the user interface on the display (e.g., 450 in FIG. 4) ofthe multifunction device when the touch-sensitive surface is separatefrom the display. It should be understood that similar methods may beused for other user interfaces described herein.

Attention is now directed towards embodiments of handwriting inputmethods and user interfaces (“UI”) that may be implemented on amultifunction device (e.g., device 100).

FIG. 5 is a block diagram illustrating an exemplary handwriting inputmodule 157 that interacts with the I/O interface module 500 (e.g., I/Ointerface 330 in FIG. 3 or I/O subsystem 106 in FIG. 1) to providehandwriting input capabilities on the device in accordance with someembodiments. As shown in FIG. 5, the handwriting input module 157includes an input processing module 502, a handwriting recognitionmodule 504, and a result generation module 506. In some embodiments, theinput processing module 502 includes a segmentation module 508, and anormalization module 510. In some embodiments, the result generationmodule 506 includes a radical clustering module 512 and one or morelanguage models 514.

In some embodiments, the input processing module 502 communicates withthe I/O interface module 500 (e.g., I/O interface 330 in FIG. 3 or I/Osubsystem 106 in FIG. 1) to receive handwriting inputs from a user.Handwriting is input via any suitable means, such as a touch-sensitivedisplay system 112 in FIG. 1 and/or a touchpad 355 in FIG. 3. Thehandwriting inputs include data representing each stroke provided by theuser within a predetermined handwriting input area within thehandwriting input UI. In some embodiments, the data representing eachstroke of the handwriting input includes data such as the start and endlocations, the intensity profile, and the motion path of a sustainedcontact (e.g., a contact between the user's finger or a stylus and thetouch-sensitive surface of the device) within the handwriting inputarea. In some embodiments, the I/O Interface module 500 passes thesequences of handwritten strokes 516 with associated temporal andspatial information to the input processing module 502 in real-time. Atthe same time, the I/O Interface module also provides real-timerendering 518 of the handwritten strokes within the handwriting inputarea of the handwriting input user interface as visual feedback to theuser's input.

In some embodiments, as the data representing each handwritten stroke isreceived by the input processing module 502, the temporal and sequenceinformation associated with multiple consecutive strokes is alsorecorded. For example, the data optionally includes a stack showing theshape, size, spatial saturation of the individual strokes withrespective stroke sequence numbers, and relative spatial locations ofthe strokes along a writing direction of the entire handwriting input,etc. In some embodiments, the input processing module 502 providesinstructions back to the I/O interface modules 500 to render thereceived strokes on a display 518 (e.g., display 340 in FIG. 3 ortouch-sensitive display 112 in FIG. 1) of the device. In someembodiments, the rendering of the received strokes is animated toprovide a visual effect mimicking actual progress of writing on awriting surface (e.g., a sheet of paper) with a writing instrument(e.g., a pen). In some embodiments, the user is optionally allowed tospecify the pen-tip style, color, texture, etc. of the rendered strokes.

In some embodiments, the input processing module 502 processes thestrokes currently accumulated in the handwriting input area to assignthe strokes into one or more recognition units. In some embodiments,each recognition unit corresponds to a character that is to berecognized by the handwriting recognition model 504. In someembodiments, each recognition unit corresponds to an output character ora radical that is to be recognized by the handwriting recognition model504. A radical is a recurring component that is found in multiplecomposite logographic characters. A composite logographic character mayinclude two or more radicals arranged in accordance with a common layout(e.g., a left-right layout, a top-bottom layout, etc.). In one example,a single Chinese character “

” is constructed using two radicals, i.e., a left radical “

” and a right radical “

”.

In some embodiments, the input processing module 502 relies on thesegmentation module to assign or divide the currently accumulatedhandwritten strokes into one or more recognition units. For example,when segmenting the strokes for the handwritten character “

”, the segmentation module 508 optionally assigns the strokes clusteredon the left side of handwriting input to one recognition unit (i.e., forthe left radical “

”), and the strokes clustered on the right side of the handwriting inputto another recognition unit (i.e., for the right radical “

”). Alternatively, the segmentation module 508 may also assign all ofthe strokes into a single recognition unit (i.e., for the character “

”).

In some embodiments, the segmentation module 508 segments the currentlyaccumulated handwriting input (e.g., one or more handwritten strokes)into a group of recognition units in several different ways to create asegmentation lattice 520. For example, suppose a total of nine strokeshave been accumulated in the handwriting input area so far. According toa first segmentation chain of the segmentation lattice 520, strokes 1,2, 3 are grouped into a first recognition unit 522, and strokes 4, 5, 6are grouped into a second recognition unit 526. According to a secondsegmentation chain of the segmentation lattice 520, all of strokes 1-9are grouped into one recognition unit 526.

In some embodiments, each segmentation chain is given a segmentationscore to measure the likelihood that the particular segmentation chainis a correct segmentation of the current handwriting input. In someembodiments, factors that are optionally used to calculate thesegmentation score of each segmentation chain include: absolute and/orrelative size of the stroke, relative and/or absolute span of the strokein various directions (e.g., x, y, z directions), average of and/orvariations in the saturation level of the stroke, absolute and/orrelative distances to adjacent strokes, absolute and/or relativelocations of the strokes, the order or sequence by which the strokes areentered, the duration of each stroke, average of and/or variations inthe speed (or tempo) by which each stroke has been entered, theintensity profile of each stroke along the length of the stroke, etc. Insome embodiments, one or more functions or transformations areoptionally applied to one or more of these factors to generate thesegmentation scores of the different segmentation chains in thesegmentation lattice 520.

In some embodiments, after the segmentation module 508 has segmented thecurrent handwriting input 516 received from the user, the segmentationmodule 508 passes the segmentation lattice 520 to the normalizationmodule 510. In some embodiments, the normalization module 510 generatesan input image (e.g., input images 528) for each recognition unit (e.g.,recognition units 522, 524, and 526) specified in the segmentationlattice 520. In some embodiments, the normalization module performs thenecessary or desired normalization (e.g., stretching, cropping,down-sample or up-sampling) to the input image, such that the inputimage can be provided to the handwriting recognition model 504 as input.In some embodiments, each input image 528 includes the strokes assignedto one respective recognition unit, and corresponds to one character orradical that is to be recognized by the handwriting recognition module504.

In some embodiments, the input images generated by the input processingmodule 502 does not include any temporal information associated with theindividual strokes, and only spatial information (e.g. informationrepresented by the location and density of pixels in the input image)are preserved in the input image. A handwriting recognition modeltrained purely on spatial information of the training writing samples iscapable of handwriting recognition based on spatial information alone.As a result, the handwriting recognition model is stroke-order andstroke-direction independent, without exhaustively enumerating allpossible permutations of stroke-orders and stroke-directions for allcharacters in its vocabulary (i.e., all output classes) during training.In fact, in some embodiments, the handwriting recognition module 502does not differentiate the pixels belonging to one stroke versus anotherwithin the input image.

As will be explained in more detail later (e.g., with respect to FIGS.25A-27), in some embodiments, some temporally-derived strokedistribution information is reintroduced into a purely-spatialhandwriting recognition model to improve recognition accuracy withoutcompromising the stroke-order, and stroke-direction independence of therecognition model.

In some embodiments, the input image generated by the input processingmodule 502 for one recognition unit does not overlap with the inputimage of any other recognition unit in the same segmentation chain. Insome embodiments, input images generated for different recognition unitsmay have some overlap. In some embodiments, some overlap between inputimages is permitted for recognizing handwriting input written in acursive writing style and/or including run-on characters (e.g., onestroke connecting two adjacent characters).

In some embodiments, some normalization is performed beforesegmentation. In some embodiments, the functions of the segmentationmodule 508 and the normalization module 510 may be performed by the samemodule or two or more other modules.

In some embodiments, as the input image 528 of each recognition unit isprovided to the handwriting recognition model 504 as input, thehandwriting recognition model 504 produces an output consisting ofdifferent likelihood of the recognition unit being a respective outputcharacter in the repertoire or vocabulary (i.e., the list of allcharacters and radicals recognizable by the handwriting recognitionmodule 504) of handwriting recognition model 504. As will be explainedin more detail later, the handwriting recognition model 504 has beentrained to recognize a large number of characters in multiple scripts(e.g., at least three non-overlapping scripts that have been encoded bythe Unicode standard). Examples of non-overlapping scripts include theLatin script, Chinese characters, Arabic letters, Farsi, Cyrillic, andartificial scripts such as emoji characters. In some embodiments, thehandwriting recognition model 504 produces one or more output charactersfor each input image (i.e., for each recognition unit), and assigns arespective recognition score for each output character based on theconfidence level associated with the character recognition.

In some embodiments, the handwriting recognition model 504 generates acandidate lattice 530 in accordance with the segmentation lattice 520,where each arc in a segmentation chain (e.g., corresponding to arespective recognition unit 522, 524, 526) in the segmentation lattice520 is expanded into one or more candidate arcs (e.g., arcs 532, 534,536, 538, 540 each corresponding to a respective output character)within the candidate lattice 530. Each candidate chain within thecandidate lattice 530 is scored according to the respective segmentationscore of the segmentation chain underlying the candidate chain, and therecognition scores associated with the output characters in thecharacter chain.

In some embodiments, after the handwriting recognition model 504produces the output characters from the input images 528 of therecognition units, the candidate lattice 530 is passed to the resultgeneration module 506 to generate one or more recognition results forthe currently accumulated handwriting input 516.

In some embodiments, the result generation module 506 utilizes theradical clustering module 512 to combine one or more radicals in acandidate chain into a composite character. In some embodiments, theresult generation module 506 uses one or more language models 514 todetermine whether a character chain in the candidate lattice 530 is alikely sequence in a particular language represented by the languagemodels. In some embodiments, the result generation module 506 generatesa revised candidate lattice 542 by eliminating particular arcs orcombining two or more arcs in the candidate lattice 530.

In some embodiments, the result generation module 506 generates anintegrated recognition score for each character sequence still remainingin the revised candidate lattice 542 (e.g., character sequences 544 and546), based on the recognition scores of the output characters in thecharacter sequence, as modified (e.g., augmented or diminished) by theradical clustering module 512 and language models 514. In someembodiments, the result generation module 506 ranks the differentcharacter sequences remaining in the revised candidate lattice 542 basedon their integrated recognition scores.

In some embodiments, the result generation module 506 sends thetop-ranked character sequences as ranked recognition results 548 to theI/O interface module 500 to display to the user. In some embodiments,the I/O interface module 500 displays the received recognition results548 (e.g., “

” and “

”) in a candidate display area of the handwriting input interface. Insome embodiments, the I/O interface module displays multiple recognitionresults (e.g., “

” and “

”) for the user, and allows the user to select a recognition result toenter as a text input for a relevant application. In some embodiments,the I/O interface module automatically enters a top-ranked recognitionresult (e.g., “

”) in response to other inputs or indications of user confirmation ofthe recognition result. Effective automatic entry of a top-ranked resultcan improve the efficiency of the input interface and provide a betteruser experience.

In some embodiments, the result generation module 506 uses other factorsto alter the integrated recognition scores of the candidate chains. Forexample, in some embodiments, the result generation module 506optionally maintains a log of most frequently used characters for aparticular user, or a multitude of users. The result generation module506 optionally boosts the integrated recognition scores of particularcandidate characters or character sequences, if the particular candidatecharacters or character sequences are found among the list of mostfrequently used characters or character sequences.

In some embodiments, the handwriting input module 157 provides real-timeupdates for the recognition results displayed to the user. For example,in some embodiments, for each additional stroke entered by the user, theinput processing module 502 optionally re-segments the currentlyaccumulated handwriting input, and revises the segmentation lattice andinput images provided to the handwriting recognition model 504. In turn,the handwriting recognition model 504 optionally revises the candidatelattice provided to the result generation module 506. As a result, theresult generation module 506 optionally updates the recognition resultspresented to the user. As used in this specification, real-timehandwriting recognition refers to handwriting recognition in whichhandwriting recognition results are presented to the userinstantaneously or within a short time period (e.g., within tens ofmilliseconds to seconds). Real-time handwriting recognition differs fromoffline recognition (e.g., as in offline optical character-recognition(OCR) applications) in that recognition is initiated immediately andperformed substantially contemporaneously with receipt of thehandwriting input, rather than at a time after the current user sessionfrom a recorded image that is saved for later retrieval. In addition,offline character recognition is performed without any temporalinformation regarding individual strokes and stroke sequences, and thussegmentation is performed without the benefit of such information.Further disambiguation between similar-looking candidate characters arealso without the benefit of such temporal information.

In some embodiments, the handwriting recognition model 504 isimplemented as a convolutional neural network (CNN). FIG. 6 illustratesan exemplary convolutional neural network 602 trained on a multi-scripttraining corpus 604 containing writing samples for characters inmultiple non-overlapping scripts.

As shown in FIG. 6, the convolutional neural network 602 includes aninput plane 606, and output plane 608. Between the input plane 606 andthe output plane 608 reside a plurality of convolutional layers 610(e.g., including a first convolutional layer 610 a, zero or moreintermediate convolutional layers (not shown), and a last convolutionallayer 610 n). Each convolutional layer 610 is followed by a respectivesub-sampling layer 612 (e.g., a first sub-sampling layer 612 a, zero ormore intermediate sub-sampling layers (not shown), and a lastsub-sampling layer 612 n). After the convolutional layers and thesub-sampling layers and right before the output plane 608 resides ahidden layer 614. The hidden layer 614 is the last layer before theoutput plane 608. In some embodiments, a kernel layer 616 (e.g.,including a first kernel layer 616 a, zero or more intermediate kernellayers (not shown), and a last kernel layer 612 n) is inserted beforeeach convolutional layer 610 to improve computation efficiency.

As shown in FIG. 6, the input plane 606 receives an input image 614 of ahandwritten recognition unit (e.g., a handwritten character or radical),and the output plane 608 outputs a set of probabilities indicating thelikelihood that the recognition unit belongs to respective output class(e.g., a particular character among an output character set that theneural network is configured to recognize). The output classes of theneural network as a whole (or the output character set of the neuralnetwork) are also referred to as the repertoire or vocabulary of thehandwriting recognition model. The convolutional neural networkdescribed herein can be trained to have a repertoire of tens ofthousands of characters.

When an input image 614 is processed through the different layers of theneural network, different spatial features embedded in the input image614 are extracted by the convolutional layers 610. Each convolutionallayer 610 is also referred to as a set of feature maps and act asfilters for picking out particular features in the input image 614 fordifferentiating between the images corresponding to differentcharacters. The sub-sampling layers 612 ensure that features on anincreasingly larger scale are captured from the input image 614. In someembodiments, the sub-sampling layers 612 are implemented using amax-pooling technique. The max-pooling layers create position invarianceover larger local regions and down samples the output image of thepreceding convolutional layer by a factor of Kx and Ky along eachdirection, Kx and Ky being the size of the max-pooling rectangle.Max-pooling leads to a faster convergence rate by selecting superiorinvariant features which improves generalization performances. In someembodiments, sub-sampling is achieved using other methods.

In some embodiments, after the last set of convolutional layer 610 n andsub-sampling layer 612 n and before the output plane 608 resides afully-connected layer, namely the hidden layer 614. The fully-connectedhidden layer 614 is a multi-layer perceptron that fully connects thenodes in the last sub-sampling layer 612 n and the nodes in the outputplane 608. The hidden layer 614 takes the output images received fromthe layer before and through logistic regression reaches one of theoutput characters in the output layer 608.

During training of the convolutional neural network 602, features andrespective weights associated with the features in the convolutionallayers 610, as well as weights associated with the parameters in thehidden layer 614 are tuned such that classification errors are minimizedfor the writing samples with known output classes in the training corpus604. Once the convolutional neural network 602 has been trained, and theoptimal set of parameters and associated weights have been establishedfor the different layers in the network, the convolutional neuralnetwork 602 can be used to recognize new writing samples 618 that arenot part of the training corpus 604, such as input images generatedbased on real-time handwriting input received from the user.

As described in herein, the convolutional neural network of ahandwriting input interface is trained using a multi-script trainingcorpus to enable multi-script or mixed-script handwriting recognition.In some embodiments, the convolutional neural network is trained torecognize a large repertoire of 30 thousand to over 60 thousandcharacters (e.g., all characters encoded by the Unicode standard). Moststate-of-the-art handwriting recognition systems are based onstroke-order dependent Hidden Markov Methods (HMMs). In addition, mostexisting handwriting recognition models are language-specific, andinclude a small repertoire of tens of characters (e.g., characters ofthe English alphabet, the Greek alphabet, all ten digits, etc.), up to afew thousand of characters (e.g., a set of most commonly used Chinesecharacter). As such, the universal recognizer described herein canhandle orders of magnitudes more characters than most existing systems.

Some conventional handwriting systems may include several individuallytrained handwriting recognition models, each tailored for a particularlanguage or a small set of characters. A writing sample is propagatedthrough the different recognition models until a classification can bemade. For example, the handwriting sample may be provided to a series ofconcatenated language-specific or script-specific character recognitionmodels, if the handwriting sample cannot be conclusively classified by afirst recognition model, it is provided to a next recognition model,which attempts to classify the handwriting sample within its ownrepertoire. The approach for classification is time consuming, and thememory requirement increases quickly with each additional recognitionmodel that needs to be employed.

Other state-of-the art models require the user to specify a preferredlanguage, and use the selected handwriting recognition model to classifythe current input. Such implementations not only are cumbersome to useand consume significant memory, but also cannot be used to recognizemixed language input. Requiring the user to switch language preferencesin the middle of inputting a mixed-language or mixed-script input isimpractical.

The multi-script or universal recognizer described herein addresses atleast some of the above issues with the conventional recognitionsystems. FIG. 7 is a flow chart of an exemplary process 700 for traininga handwriting recognition module (e.g., a convolutional neural network)using a large multi-script training corpus, such that the handwritingrecognition module can be subsequently used to provide real-timemulti-language and multi-script handwriting recognition for a user'shandwriting input.

In some embodiments, the training of the handwriting recognition modelis performed on a server device, and the trained handwriting recognitionmodel is then provided to a user device. The handwriting recognitionmodel optionally performs real-time handwriting recognition locally onthe user device without requiring further assistance from the server. Insome embodiments, both the training and the recognition is provided onthe same device. For example, a server device can receive the user'shandwriting input from a user device, performs the handwritingrecognition, and sends the recognition results to the user device inreal-time.

In the exemplary process 700, at a device having one or more processorsand memory, the device trains (702) a multi-script handwritingrecognition model based on spatially-derived features (e.g.,stroke-order independent features) of a multi-script training corpus. Insome embodiments, the spatially-derived features of the multi-scripttraining corpus are (704) stroke-order independent and stroke-directionindependent. In some embodiments, the training of the multi-scripthandwriting recognition model is (706) independent of temporalinformation associated with respective strokes in the handwritingsamples. Specifically, images of the handwriting samples are normalizedto a predetermined size, and the images do not include any informationon the order by which individual strokes are entered to form the image.Furthermore, the images also do not include any information on thedirection by which individual strokes are entered to form the image. Infact, during training, features are extracted from the handwritingimages without regard to how the images are temporally formed by theindividual strokes. Therefore, during recognition, no temporalinformation related to the individual strokes is needed. As a result,the recognition robustly provides consistent recognition results despiteof delayed, out-of-order strokes, and arbitrary stroke directions in thehandwriting input.

In some embodiments, the multi-script training corpus includeshandwriting samples corresponding to characters of at least threenon-overlapping scripts. As shown in FIG. 6, the multi-script trainingcorpus includes handwriting samples collected from many users. Eachhandwriting sample corresponds to one character of a respective scriptthat is represented the handwriting recognition model. To adequatelytrain the handwriting recognition model, the training corpus includes alarge number of writing samples for each character of the scriptsrepresented in the handwriting recognition model.

In some embodiments, the at least three non-overlapping scripts include(708) Chinese characters, emoji characters, and Latin script. In someembodiments, the multi-script handwriting recognition model has (710) atleast thirty thousand output classes, representing thirty thousandcharacters spanning at least three non-overlapping scripts.

In some embodiments, multi-script training corpus includes respectivewriting samples for each character of all Chinese characters encoded inthe Unicode standard (e.g., all or a substantial portion of all CJK(Chinese-Japanese-Korean) unified ideographs). The Unicode standarddefines a total of about seventy-four thousand CJK unified ideographs.The basic block (4E00-9FFF) of the CJK unified ideographs includes20,941 basic Chinese characters, which are used in the Chinese language,as well as in Japanese, Korean, and Vietnamese languages. In someembodiments, the multi-script training corpus includes writing samplesfor all characters in the basic block of the CJK unified ideographs. Insome embodiments, the multi-script training corpus further includeswriting samples for CJK radicals that can be used to structurallycompose one or more composite Chinese characters. In some embodiments,the multi-script training corpus further includes writing samples forless frequently used Chinese characters, such as the Chinese charactersencoded in one or more of the CJK unified ideograph extensions.

In some embodiments, the multi-script training corpus further includesrespective writing samples for each character of all characters in theLatin script encoded by the Unicode standard. The characters in thebasic Latin script include capital and small Latin letters, as well asvarious basic symbols and digits commonly used on a standard Latinkeyboard. In some embodiments, the multi-script training corpus furtherincludes characters in the extended Latin script (e.g., various accentedforms of the basic Latin letters).

In some embodiments, the multi-script training corpus includes writingsamples that correspond to each character of an artificial script thatis not associated with any natural human language. For example, in someembodiments, a set of emoji characters is optionally defined in an emojiscript, and writing samples corresponding to each of the emojicharacters are included in the multi-script training corpus. Forexample, a hand-drawn heart-shaped symbol is a handwriting sample forthe emoji character “♡” in the training corpus. Similarly, a hand-drawnsmiley face (e.g., two dots above an upturned arc) is a handwritingsample for the emoji character “

” in the training corpus. Other emoji characters includes categories oficons showing different emotions (e.g., happy, sad, angry, embarrassed,shocked, laughing, crying, frustrated, etc.), different objects andcharacters (e.g., cat, dog, bunny, heart, fruit, eye, lips, gift,flowers, candle, moon, star, etc.), and different actions (e.g.,handshake, kiss, run, dance, jump, sleep, eat, meet, love, like, vote,etc.), etc. In some embodiments, the strokes in the handwriting samplecorresponding to an emoji character are simplified and/or stylized linesof the actual lines forming the corresponding emoji character. In someembodiments, each device or application may use a different design forthe same emoji character. For example, a smiley emoji characterpresented to a female user may be different from a smiley emojicharacter presented to a male user, even if the handwriting inputsreceived from the two users are substantially the same.

In some embodiments, the multi-script training corpus also includeswriting samples for characters in other scripts, such as the Greekscript (e.g., including Greek letters and symbols), the Cyrillic script,the Hebrew script, and one or more other scripts encoded according tothe Unicode standard. In some embodiments, the at least threenon-overlapping scripts included in the multi-script training corpusinclude Chinese characters, emoji characters, and characters in theLatin script. Chinese characters, emoji characters, and Characters inthe Latin script are naturally non-overlapping scripts. Many otherscripts may overlap with one another for at least some characters. Forexample, some characters (e.g., A, Z) in the Latin script may be foundin many other scripts (e.g., Greek, and Cyrillic). In some embodiments,the multi-script training corpus includes Chinese characters, Arabicscript, and Latin script. In some embodiments, the multi-script trainingcorpus includes other combinations of overlapping and/or non-overlappingscripts. In some embodiments, the multi-script training corpus includeswriting samples for all characters encoded by the Unicode standard.

As shown in FIG. 7, in some embodiments, to train the multi-scripthandwriting recognition model, the device provides (712) the handwritingsamples of the multi-script training corpus to a single convolutionalneural network having a single input plane and a single output plane.The device determines (714) using the convolutional neural network, thespatially-derived features (e.g., stroke-order independent features) ofthe handwriting samples and respective weights for the spatially-derivedfeatures for differentiating characters of the at least threenon-overlapping scripts represented in the multi-script training corpus.The multi-script handwriting recognition model differs from conventionalmulti-script handwriting recognition models in that, a singlehandwriting recognition model having a single input plane and a singleoutput plane is trained using all samples in the multi-script trainingcorpus. A single convolutional neural network is trained to distinguishall characters represented in the multi-script training corpus, withoutrelying on individual sub-networks that each handles a small subset ofthe training corpus (e.g., sub-networks each trained for recognizingcharacters of a particular script or characters used in a particularlanguage). In addition, the single convolutional neural network istrained to distinguish a large number of characters spanning multiplenon-overlapping scripts, rather than characters of a few overlappingscripts, such as the Latin script and the Greek script (e.g., withoverlapping letters A, B, E, Z, etc.).

In some embodiments, the device provides (716) real-time handwritingrecognition for a user's handwriting input using the multi-scripthandwriting recognition model that has been trained on thespatially-derived features of the multi-script training corpus. In someembodiments, providing real-time handwriting recognition for a user'shandwriting input includes continuously revising a recognition outputfor the user's handwriting input as the user continues to provideadditions and revisions of the handwriting input. In some embodiments,providing real-time handwriting recognition for a user's handwritinginput further includes (718) providing the multi-script handwritingrecognition model to a user device, where the user device receives ahandwriting input from a user, and locally performs handwritingrecognition on the handwriting input based on the multi-scripthandwriting recognition model.

In some embodiments, the device provides the multi-script handwritingrecognition model to a plurality of devices that have no existingoverlap in their respective input languages, and the multi-scripthandwriting recognition model is used on each of the plurality ofdevices for handwriting recognition of a different language associatedwith said each user device. For example, when the multi-scripthandwriting recognition model has been trained to recognize charactersin many different scripts and languages, the same handwritingrecognition model can be used worldwide to provide handwriting input forany of those input languages. A first device for a user who only wishesto input in English and Hebrew can use the same handwriting recognitionmodel to provide handwriting input functionality as a second device foranother user who only wishes to input in Chinese and emoji characters.Instead of requiring the user of the first device to separately installa English handwriting input keyboard (e.g., implemented with anEnglish-specific handwriting recognition model), and a separate Hebrewhandwriting input keyboard (e.g., implemented with a Hebrew-specifichandwriting recognition model), the same universal multi-scripthandwriting recognition model can be installed once on the first device,and used to provide handwriting input function for both English, Hebrew,as well as mixed input in both languages. Furthermore, instead ofrequiring the second user to install a Chinese handwriting inputkeyboard (e.g., implemented with a Chinese-specific handwritingrecognition model), and a separate emoji handwriting input keyboard(e.g., implemented with an emoji handwriting recognition model), thesame universal multi-script handwriting recognition model can beinstalled once on the second device, and used to provide handwritinginput function for both Chinese, emoji, as well as mixed input in bothscripts. Using the same multi-script handwriting model to handle a largerepertoire spanning multiple scripts (e.g., a substantial portion or allof the characters encoded in nearly one hundred different scripts)improves the utility of the recognizer without substantial burden onpart of the device suppliers and the users.

The multi-script handwriting recognition model training using a largemulti-script training corpus differ from conventional HMM-basedhandwriting recognition system, and does not rely on temporalinformation associated with individual strokes of the characters. Inaddition, the resource and memory requirement for the multi-scriptrecognition system does not increase linearly with the increase ofsymbols and languages covered by the multi-script recognition system.For example, in a conventional handwriting system, increasing the numberof languages means adding another independently trained model, and thememory requirement would be at least doubled to accommodate theincreasing capability of the handwriting recognition system. Incontrast, when the multi-script model is trained by a multi-scripttraining corpus, increasing language coverage requires retraining thehandwriting recognition model with additional handwriting samples, andincreasing the size of the output plane, but the amount of increase isvery moderate. Suppose that the multi-script training corpus includeshandwriting samples corresponding to n different languages, and themulti-script handwriting recognition model occupies a memory of size m,when increasing the language coverage to N languages (N>n), the devicere-trains the multi-script handwriting recognition model based onspatially-derived features of a second multi-script training corpus, thesecond multi-script training corpus including second handwriting samplescorresponding to the N different languages. The changes in M/m remainsubstantially constant within a range of 1-2, with the changes in N/nfrom 1 to 100. Once the multi-script handwriting recognition model hasbeen retrained, the device can provide real-time handwriting recognitionfor a user's handwriting input using the re-trained multi-scripthandwriting recognition model.

FIGS. 8A-8B show exemplary user interfaces for providing real-time,multi-script handwriting recognition and input on a portable user device(e.g., device 100). In FIGS. 8A-8B, the handwriting input interface 802is displayed on a touch-sensitive display screen (e.g., touch screen112) of the user device. The handwriting input interface 802 includes ahandwriting input area 804, a candidate display area 806, and a textinput area 808. In some embodiments, the handwriting input interface 802further includes a plurality of control elements, where each can beinvoked to cause the handwriting input interface to perform apredetermined function. As shown in FIG. 8A, a delete button, a spacebutton, a carriage return or Enter button, a keyboard switching buttonare included in the handwriting input interface. Other control elementsare possible, and can be optionally provided in the handwriting inputinterface to suit each different application utilizing the handwritinginput interface 802. The layout of the different components of thehandwriting input interface 802 is merely illustrative, and can vary fordifferent devices and different applications.

In some embodiments, the handwriting input area 804 is a touch-sensitivearea for receiving handwriting input from the user. A sustained contactand its associated motion path on the touch screen within thehandwriting input area 804 are registered as a handwritten stroke. Insome embodiments, the handwritten stroke registered by the device isvisually rendered within the handwriting input area 804 at the samelocations traced by the sustained contact. As shown in FIG. 8A, the userhas provided a number of handwritten strokes in the handwriting inputarea 804, including some handwritten Chinese characters (e.g., “

”), some handwritten English letters (e.g., “Happy”), and a hand-drawnemoji character (e.g., a smiley). The handwritten characters aredistributed in multiple lines (e.g., two lines) in the handwriting inputarea 804.

In some embodiments, the candidate display area 806 displays one or morerecognition results (e.g., 810 and 812) for the handwriting inputcurrently accumulated in the handwriting input area 804. In general, thetop-ranked recognition result (e.g., 810) is displayed in the firstposition in the candidate display area. As shown in FIG. 8A, since thehandwriting recognition model described herein is capable of recognizingcharacters of multiple non-overlapping scripts including Chinesecharacters, the Latin script, and emoji characters, the recognitionresult (e.g., 810) provided by the recognition model correctly includesthe Chinese characters, English letters, and the emoji characterrepresented by the handwriting input. The user is not required to stopin the middle of writing the input to choose or switch the recognitionlanguages.

In some embodiments, the text input area 808 is an area that displaystext input provided to a respective application that is employing thehandwriting input interface. As shown in FIG. 8A, the text input area808 is used by a Notes application, and text (e.g., “America

”) currently shown within the text input area 808 is text input alreadyprovided to the Notes application. In some embodiments, a cursor 813indicates a current text input position in the text input area 808.

In some embodiments, a user can select a particular recognition resultdisplayed in the candidate display area 806, e.g., by an explicitselection input (e.g., a tap gesture on one of the displayed recognitionresult), or an implicit confirmation input (e.g., a tap gesture on the“Enter” button or a double tap gesture in the handwriting input area).As shown in FIG. 8B, the user has explicitly selected the top-rankedrecognition result 810 using a tap gesture (as indicated by a contact814 over the recognition result 810 in FIG. 8A). In response to theselection input, text of the recognition result 810 is inserted at theinsertion point indicated by the cursor 813 in the text input area 808.As shown in FIG. 8B, once the text of the selected recognition result810 has been entered into the text input area 808, the handwriting inputarea 804 and the candidate display area 806 are both cleared. Thehandwriting input area 804 is now ready to accept a new handwritinginput, and the candidate display area 806 can now be used to displayrecognition results for the new handwriting input. In some embodiments,an implicit confirmation input causes the top-ranked recognition resultto be entered into the text input area 808 without requiring the user tostop and select the top-ranked recognition result. A well-designedimplicit confirmation input improves text entry speed and reducescognitive burden placed on the user during text composition.

In some embodiments (not shown in FIGS. 8A-8B), the top-rankedrecognition result of a current handwriting input is optionallytentatively displayed in the text input area 808. The tentative textinput shown in the text input area 808 is visually distinguished fromother text input in the text input area, e.g., by a tentative input boxsurrounding the tentative text input. The text shown in the tentativeinput box is not yet committed or provided to the associated application(e.g., the Notes application), and is automatically updated when thetop-ranked recognition result is changed by the handwriting inputmodule, e.g., in response to user revision of the current handwritinginput.

FIGS. 9A-9B are flow charts of an exemplary process 900 for providingmulti-script handwriting recognition on a user device. In someembodiments, as shown in FIG. 900, the user device receives (902) amulti-script handwriting recognition model, the multi-script recognitionmodel having been trained on spatially-derived features (e.g.,stroke-order and stroke-direction independent features) of amulti-script training corpus, the multi-script training corpus includinghandwriting samples corresponding to characters of at least threenon-overlapping scripts. In some embodiments, the multi-scripthandwriting recognition model is (906) a single convolutional neuralnetwork having a single input plane and a single output plane, andincludes spatially-derived features and respective weights for thespatially-derived features for differentiating characters of the atleast three non-overlapping scripts represented in the multi-scripttraining corpus. In some embodiments, the multi-script handwritingrecognition model is (908) configured to recognize characters based onrespective input images of one or more recognition units identified inthe handwriting input, and respective spatially-derived features usedfor recognition are independent of respective stroke order, strokedirection, and continuity of strokes in the handwriting input.

In some embodiments, the user device receives (908) a handwriting inputfrom a user, the handwriting input including one or more handwrittenstrokes provided on a touch-sensitive surface coupled to the userdevice. For example, the handwriting input includes respective data onthe location and movement of a contact between a finger or stylus andthe touch-sensitive surface coupled to the user device. In response toreceiving the handwriting input, the user device provides (910) inreal-time one or more handwriting recognition results to the user basedon the multi-script handwriting recognition model that has been trainedon the spatially-derived features of the multi-script training corpus(912).

In some embodiments, when providing real-time handwriting recognitionresults to the user, the user device segments (914) the user'shandwriting input into one or more recognition units, each recognitionunit including one or more of the handwritten strokes provided by theuser. In some embodiments, the user device segments the user'shandwriting input according to the shape, location, and size of theindividual strokes made by the contact between the user's finger orstylus and the touch-sensitive surface of the user device. In someembodiments, the segmentation of the handwriting input further takesinto account of the relative order, and relative position of theindividual strokes made by the contact between the user's finger orstylus and the touch-sensitive surface of the user device. In someembodiments, the user's handwriting input is in a cursive writing style,and each continuous stroke in the handwriting input may correspond tomultiple strokes in a recognized character in print form. In someembodiments, the user's handwriting input may include a continuousstroke spanning multiple recognized characters in printed form. In someembodiments, the segmentation of the handwriting input generates one ormore input images each corresponding to a respective recognition unit.In some embodiments, some of the input images optionally include someoverlapping pixels. In some embodiments, the input images do not includeany overlapping pixels. In some embodiments, the user device generates asegmentation lattice, each segmentation chain of the segmentationlattice represents a respective way of segmenting the currenthandwriting input. In some embodiments, each arc in a segmentation chaincorresponds to a respective group of strokes in the current handwritinginput.

As shown in FIG. 900, the user device provides (914) a respective imageof each of the one or more recognition units as an input to themulti-script recognition model. For at least one of the one or morerecognition units, the user device obtains (916) from the multi-scripthandwriting recognition model at least a first output character from afirst script and at least a second output from a second script differentfrom the first script. For example, the same input image may cause themulti-script recognition model to output two or more similar lookingoutput characters from different scripts as recognition results for thesame input image. For example, the handwriting inputs for the letter “a”in the Latin script and the character “α” in the Greek script are oftensimilar. Furthermore, the handwriting inputs for the letter “J” in theLatin script and the Chinese character “

” are often similar. Similarly, the handwriting input for the emojicharacter “

” may be similar to the handwriting input for the CJK radical “

”. In some embodiments, the multi-script handwriting recognition modeloften produces multiple candidate recognition results that are likelycorrespond to the user's handwriting input, because the visualappearance of the handwriting input would be difficult even for a humanreader to decipher. In some embodiments, the first script is the CJKbasic character block and the second script is the Latin script asencoded by the Unicode standard. In some embodiments, the first scriptis CJK basic character block, and the second script is a set of emojicharacters. In some embodiments, the first script is the Latin script,and the second script is the emoji characters.

In some embodiments, the user device displays (918) both the firstoutput character and the second output character in a candidate displayarea of the handwriting input interface of the user device. In someembodiments, the user device selectively displays (920) one of the firstoutput character and the second output character based on which one ofthe first and second scripts is a respective script used in a softkeyboard currently installed on the user device. For example, supposethe handwriting recognition model has identified the Chinese character “

” and the Greek letter “λ” as the output characters for the currenthandwriting input, the user device determines whether the user hasinstalled a Chinese soft keyboard (e.g., a keyboard using the Pinyininput method) or the Greek input keyboard on the user device. If theuser device determines that only the Chinese soft keyboard has beeninstalled, the user device optionally displays only the Chinesecharacter “

” and not the Greek letter “λ” as the recognition result to the user.

In some embodiments, the user device provides real-time handwritingrecognition and input. In some embodiments, the user device continuouslyrevises (922) one or more recognition results for the user's handwritinginput in response to continued additions to or revisions of thehandwriting input by the user, before the user makes an explicit orimplicit selection of a recognition result displayed to the user. Insome embodiments, in response to each revision of the one or morerecognition results, the user displays (924) the respective revised oneor more recognition results to the user in a candidate display area ofthe handwriting input user interface.

In some embodiments, the multi-script handwriting recognition model is(926) trained to recognize all characters of at least threenon-overlapping scripts including Chinese characters, emoji characters,and the Latin script encoded according to the Unicode standard. In someembodiments, the at least three non-overlapping scripts include Chinesecharacters, the Arabic script, and the Latin script. In someembodiments, the multi-script handwriting recognition model has (928) atleast thirty thousand output classes, representing at least thirtycharacters spanning the at least three non-overlapping scripts.

In some embodiments, the user device allows the user to enter amulti-script handwriting input, such as a phrase that includescharacters in more than one script. For example, the user may writecontinuously and receives handwriting recognition results includingcharacters in more than one script, without stopping in the middle ofwriting to manually switch the recognition language. For example, theuser may write the multi-script sentence “Hello means

in Chinese.” in the handwriting input area of the user device, withouthaving to switch the input language from English to Chinese beforewriting the Chinese characters “

” or switching the input language back from Chinese to English whenwriting the English words “in Chinese.”

As described herein, the multi-script handwriting recognition model isused to provide real-time handwriting recognition for a user's input. Insome embodiments, the real-time handwriting recognition is used toprovide real-time multi-script handwriting input functionality on auser's device. FIGS. 10A-10C are flow charts of an exemplary process1000 for providing real-time handwriting recognition and input on a userdevice. Specifically, the real-time handwriting recognition isstroke-order independent on a character-level, a phrase level, and asentence level.

In some embodiments, stroke-order independent handwriting recognition ona character level requires that the handwriting recognition modelprovides the same recognition result for a particular handwrittencharacter, regardless of the sequence by which the individual strokes ofthe particular character has been provided by the user. For example,Individual strokes of a Chinese character are typically written in aparticular order. Although native speakers of Chinese are often trainedto write each character in a particular order in school, many users havelater adopted personalized styles and stroke sequences that depart fromthe conventional stroke order. In addition, cursive writing styles arehighly individualized, and multiple strokes in a printed form of aChinese character are often merged into a single stylized stroke thattwists and turns, and sometimes even runs on to a next Character. Astroke-order independent recognition model is trained based on images ofwriting samples that is free of temporal information associated withindividual strokes. Therefore, the recognition is independent ofstroke-order information. For example, for the Chinese character “

”, the same recognition result “

” will be given by the handwriting recognition model regardless ofwhether the user wrote the horizontal stroke first or the verticalstroke first.

As show in FIG. 10A, in the process 1000, the user device receives(1002) a plurality of handwritten strokes from a user, the plurality ofhandwritten strokes corresponding to a handwritten character. Forexample, the handwriting input for the character “

” typically includes a substantially horizontal handwritten strokeintersecting a substantially vertical handwritten stroke.

In some embodiments, the user device generates (1004) an input imagebased on the plurality of handwritten strokes. In some embodiments, theuser device provides (1006) the input image to a handwriting recognitionmodel to perform real-time handwriting recognition of the handwrittencharacter, where the handwriting recognition model provides stroke-orderindependent handwriting recognition. The user device then displays(1008) in real-time of receiving the plurality of handwritten strokes,an identical first output character (e.g., the character “

” in printed form) irrespective of a respective order by which theplurality of handwritten strokes (e.g., the horizontal stroke and thevertical stroke) have been received from the user.

Although some conventional handwriting recognition system permits minorstroke-order variations in a small number of characters, by specificallyincluding such variations in the training of the handwriting recognitionsystem. Such conventional handwriting recognition systems are notscalable to accommodate arbitrary stroke-order variations in a largenumber of complex characters, such as Chinese characters, because even aCharacter of moderate complexity would already give rise to a largenumber of variations in stroke order. Furthermore, by merely includingmore permutations of acceptable stroke orders for particular characters,the conventional recognition systems still would not be able to handlehandwriting inputs in which multiple strokes are combined into a singlestroke (e.g., as in writing of a super cursive style) or in which onestroke is broken down into multiple sub-strokes (e.g., as in a charactercaptured with super coarse sampling of the input stroke). Therefore, themulti-script handwriting system that is trained on spatially-derivedfeatures as described herein provides advantages over the conventionalrecognition systems.

In some embodiments, stroke-order independent handwriting recognition isperformed independent of temporal information associated with individualstrokes within each handwritten character. In some embodiments,stroke-order independent handwriting recognition is performed inconjunction with stroke-distribution information which takes intoaccount of spatial distribution of individual strokes before they aremerged into a flat input image. More details on how thetemporally-derived stroke-distribution information is used to augmentthe stroke-order independent handwriting recognition described above areprovided later in the specification (e.g., with respect to FIGS.25A-27). The technique described with respect to FIGS. 25A-27 does notdestroy the stroke-order independence of the handwriting recognitionsystem.

In some embodiments, the handwriting recognition model provides (1010)stroke-direction independent handwriting recognition. In someembodiments, stroke-direction independent recognition requires that theuser device displays in response to receiving the plurality ofhandwriting inputs, the identical first output character irrespective ofa respective stroke direction by which each of the plurality ofhandwritten strokes have been provided by the user. For example, if theuser has written the Chinese character “ ” in the handwriting input areaof the user device, the handwriting recognition model would output thesame recognition result, regardless of whether the user has drawn thehorizontal stroke from left to right or from right to left. Similarly,the handwriting recognition model would output the same recognitionresult, regardless of whether the user has drawn the vertical stroke inthe downward direction or in the upward direction. In another example,many Chinese characters are structurally made of two or more radicals.Some Chinese characters each include a left radical and a right radical,and people customarily write the left radical first, and the rightradical second. In some embodiments, the handwriting recognition modelwould provide the same recognition result regardless of whether the userhas written the right radical or the left radical first, as long as theresulting handwriting input shows the left radical to the left of theright radical when the user completes the handwritten character.Similarly, some Chinese characters each include a top radical and abottom radical, and people customarily write the top radical first, andthe bottom radical last. In some embodiments, the handwritingrecognition model would provide the same recognition result regardlessof whether the user has written the top radical or the bottom radicalfirst, as long as the resulting handwriting input shows the top radicalabove the bottom radical. In other words, the handwriting recognitionmodel does not rely on the directions by which the user provides theindividual strokes of the handwritten character to determine theidentity of the handwritten character.

In some embodiments, the handwriting recognition model provideshandwriting recognition based on the image of a recognition unit,regardless of the number of sub-strokes by which the recognition unithas been provided by the user. In other words, in some embodiments, thehandwriting recognition model provides (1014) stroke-count independenthandwriting recognition. In some embodiments, the user device displaysin response to receiving the plurality of handwritten strokes, theidentical first output character irrespective of how many handwrittenstrokes are used to form a continuous stroke in the input image. Forexample, if the user has written the Chinese character “+” in thehandwriting input area, the handwriting recognition model outputs thesame recognition result, regardless of whether the user has providedfour strokes (e.g., two short horizontal strokes and two short verticalstrokes to make up the cross-shaped character), or two strokes (e.g., anL-shaped stroke and a 7-shaped stroke, or a horizontal stroke and avertical stroke), or any other number of strokes (e.g., hundreds ofextremely short strokes or dots) to make up the shape of the character “

”.

In some embodiments, not only is the handwriting recognition modelcapable of recognizing the same character regardless of the order,direction, and stroke-count by which each single character has beenwritten, the handwriting recognition model is also capable ofrecognizing multiple characters regardless of the temporal order bywhich the strokes of the multiple characters have been provided by theuser.

In some embodiments, the user device has not only received the firstplurality of handwritten strokes, but also received (1016) a secondplurality of handwritten strokes from the user, where the secondplurality of handwritten strokes correspond to a second handwrittencharacter. In some embodiments, the user device generates (1018) asecond input image based on the second plurality of handwritten strokes.In some embodiments, the user device provides (1020) the second inputimage to the handwriting recognition model to perform real-timerecognition of the second handwritten character. In some embodiments,the user device displays (1022) in real-time of receiving the secondplurality of handwritten strokes, a second output charactercorresponding to the second plurality of handwritten strokes. In someembodiments, the second output character and the first output characterare concurrently displayed in a spatial sequence independent of arespective order by which the first plurality of handwritten strokes andthe second plurality of handwritten strokes have been provided by theuser. For example, if the user has written two Chinese characters (e.g.,“

” and “

”) in the handwriting input area of the user device, the user devicewill display the recognition result “

” regardless of whether the user has written strokes of the character “

” or the strokes of the character “

” first, as long as the handwriting input currently accumulated in thehandwriting input area shows the strokes for the character “

” to the left of the strokes for the character “

”. In fact, even if the user has written some of the strokes (e.g., theleft-slanted stroke) for the character “

” before some of the strokes (e.g., the vertical stroke) for thecharacter “

”, as long as the resulting image of the handwriting input in thehandwriting input area shows all the strokes for the character “

” to the left of all the strokes for the character “

”, the user device will show the recognition result “

” in the spatial sequence of the two handwritten characters.

In other words, as shown in FIG. 10B, in some embodiments, the spatialsequence of the first output character and the second output charactercorresponds (1024) to a spatial distribution of the first plurality ofhandwritten strokes and the second plurality of strokes along a defaultwriting direction (e.g., from left to right) of a handwriting inputinterface of the user device. In some embodiments, the second pluralityof handwritten strokes are received (1026) temporally after the firstplurality of handwritten strokes, and the second output characterprecedes the first output character in a spatial sequence along adefault writing direction (e.g., from left to right) of a handwritinginput interface of the user device.

In some embodiments, the handwriting recognition model providesstroke-order independent recognition on a sentence to sentence level.For example, even if the handwritten character “

” is in a first handwritten sentence and the handwritten character “

” is in a second handwritten sentence, and the two handwrittencharacters are separated by one or more other handwritten charactersand/or words in the handwriting input area, the handwriting recognitionmodel would still provide the recognition result showing the twocharacters in the spatial sequence “

. . .

”. The recognition result and the spatial sequence of the two recognizedcharacters remain the same regardless of the temporal order by which thestrokes of the two characters have been provided by the user, providedthat the recognition units for the two characters are spatially arrangedin the sequence “

. . .

” when the user completes the handwriting input. In some embodiments,the first handwritten character (e.g., “

”) is provided by the user as part of a first handwritten sentence(e.g., “

is a number.”), and the second handwriting character (e.g., “

”) is provided by the user as part of a second handwritten sentence(e.g., “

is another number.”) and the first and the second handwritten sentencesare concurrently displayed in a handwriting input area of the userdevice. In some embodiments, when the user confirms that the recognitionresult (e.g., “

is a number

is another number.”) is the correct recognition result, the twosentences will be entered into a text input area of the user device, andthe handwriting input area will be cleared for the user to enter anotherhandwriting input.

In some embodiments, since the handwriting recognition model isstroke-order independent not only on a character-level, but also on aphrase level and a sentence level, the user can make corrections to apreviously uncompleted character after subsequent characters have beenwritten. For example, if the user has forgotten to write a particularstroke for a character before moving on to write one or more subsequentcharacters in the handwriting input area, the user can still put downthe missing stroke later at the right location in the particularcharacter to receive the correct recognition result.

In conventional stroke-order dependent recognition systems (e.g., anHMM-based recognition system), once a character is written, it iscommitted, and the user can no longer make any changes to it. If theuser wishes to make any changes, the user has to delete the characterand all subsequent characters to start all over again. In someconventional recognition systems, the user is required to complete ahandwritten character within a short, predetermined time window, and anystrokes entered outside of the predetermined time window would not beincluded in the same recognition unit as other strokes provided duringthe time window. Such conventional systems are difficult to use andcause much frustration for the user. A stroke-order independent systemdoes not suffer from these shortcomings, and the user can complete acharacter in any order and any time frame as the user seems fit. Theuser may also make a correction (e.g., add one or more strokes) to anearlier written character after having subsequently written one or morecharacters in the handwriting input interface. In some embodiments, theuser may also individually delete (e.g., using the methods describedlater with respect to FIGS. 21A-22B) an earlier written character andrewrite it in the same location in the handwriting input interface.

As shown in FIGS. 10B-10C, the second plurality of handwritten strokesspatially follow (1028) the first plurality of handwritten strokes alonga default writing direction of the handwriting input interface of theuser device, and the second output character follows the first outputcharacter in a spatial sequence along the default writing direction inthe candidate display area of the handwriting input interface. The userdevice receives (1030) a third handwritten stroke from the user torevise the first handwritten character (i.e., the handwritten characterformed by the first plurality of handwritten strokes), the thirdhandwritten stroke being received temporally after the first and thesecond pluralities of handwritten strokes. For example, the user haswritten two characters in a spatial sequence from left to right (e.g., “

”) in the handwriting input area. The first plurality of strokes form ahandwritten character “

” Note that, the user in fact intended to write the character “

”, but missed one stroke. The second plurality of strokes form thehandwritten character “

”. When the user later realizes that he wished to write “

” instead of “

”, the user can simply put one more vertical stroke below the strokesfor the character “

”, and the user device will assign the vertical stroke to the firstrecognition unit (e.g., the recognition unit for “

”). The user device will output a new output character (e.g., “

”) for the first recognition unit, where the new output character willreplace the previous output character (e.g., “

”) in the recognition result. As shown in FIG. 10C, in response toreceiving the third handwritten stroke, the user device assigns (1032)the third handwritten stroke to the same recognition unit as the firstplurality of handwritten strokes based on relative proximity of thethird handwritten stroke to the first plurality of handwritten strokes.In some embodiments, the user device generates (1034) a revised inputimage based on the first plurality of handwritten stroke and the thirdhandwritten stroke. The user device provides (1036) the revised inputimage to the handwriting recognition model to perform real-timerecognition of the revised handwritten character. In some embodiments,the user device displays (1040) in response to receiving the thirdhandwriting input, a third output character corresponding to the revisedinput image, where the third output character replaces the first outputcharacter and is concurrently displayed with the second output characterin the spatial sequence along the default writing direction.

In some embodiments, the handwriting recognition module recognizes thehandwriting input written in a default writing direction from left toright. For example, the user can write characters from left to right,and in one or more rows. In response to the handwriting input, thehandwriting input module presents recognition results that includecharacters in a spatial sequence from left to right, and in one or morerows as necessary. If the user selects a recognition result, theselected recognition result is inputted into the text input area of theuser device. In some embodiments, the default writing direction is fromtop to bottom. In some embodiments, the default writing direction isfrom right to left. In some embodiments, the user optionally changes thedefault writing direction to an alternative writing direction after arecognition result has been selected and the handwriting input area hasbeen cleared.

In some embodiments, the handwriting input module allows the user toenter multiple-character handwriting input in the handwriting input areaand allows deletion of strokes from the handwriting input onerecognition unit at a time, rather than all recognition units at once.In some embodiments, the handwriting input module allows deletion fromthe handwriting input one stroke at a time. In some embodiments, thedeletion of recognition unit proceeds one by one in the directionopposite to the default writing direction, regardless of the order bywhich the recognition units or strokes have been entered to produce thecurrent handwriting input. In some embodiments, the deletion of strokesproceeds one by one in the reverse order it has been entered within eachrecognition unit, and when the strokes in one recognition unit have allbeen deleted, the deletion of strokes proceed to the next recognitionunit in the direction opposite to the default writing direction.

In some embodiments, while the third output character and the secondoutput character are concurrently displayed as a candidate recognitionresult in the candidate display area of the handwriting input interface,the user device receives a deletion input from the user. In response tothe deletion input, the user device deletes the second output characterfrom the recognition result, while maintaining the third outputcharacter in the recognition result displayed in the candidate displayarea.

In some embodiments, as shown in FIG. 10C, the user device renders(1042) in real-time the first plurality of handwritten strokes, thesecond plurality of handwritten strokes, and the third handwrittenstroke as each of said handwritten stroke is provided by the user. Insome embodiments, in response to receiving the deletion input from theuser, the user device deletes (1044) a respective rendering of thesecond plurality of handwriting inputs (e.g., corresponding to thesecond handwritten character) from the handwriting input area, whilemaintaining respective renderings of the first plurality of handwrittenstrokes and the third handwritten stroke (e.g., together correspondingto the revised first handwritten character) in the handwriting inputarea. For example, after the user has provided the missing verticalstroke in the character sequence “

”, if the user enters a deletion input, the strokes in the recognitionunit for the character “

” is removed from the handwriting input area, and the character “

” is removed from the recognition result “

” in the candidate display area of the user device. After the deletion,the strokes for the character “

” remain in the handwriting input area, while the recognition resultshows only the character “

”.

In some embodiments, the handwritten character is a multi-stroke Chinesecharacter. In some embodiments, the first plurality of handwriting inputis provided in a cursive writing style. In some embodiments, the firstplurality of handwriting input is provided in a cursive writing styleand the handwritten character is a multi-stroke Chinese character. Insome embodiments, the handwritten characters are written in Arabic in acursive style. In some embodiments, the handwritten characters arewritten in other scripts in a cursive style.

In some embodiments, the user device establishes respectivepredetermined constraints on a set of acceptable dimensions for ahandwritten character input, and segments a currently accumulatedplurality of handwritten strokes into a plurality of recognition unitsbased on the respective predetermined constraints, where a respectiveinput image is generated from each of the recognition units, provided tothe handwriting recognition model, and recognized as a correspondingoutput character.

In some embodiments, the user device receives an additional handwrittenstroke from the user after having segmented the currently accumulatedplurality of handwritten strokes. The user device assigns the additionalhandwritten stroke to a respective one of the plurality of recognitionunits based on a spatial position of the additional handwritten strokerelative to the plurality of recognition units.

Attention is now turned to exemplary user interfaces for providinghandwriting recognition and input on a user device. In some embodiments,the exemplary user interfaces are provided on a user device based on amulti-script handwriting recognition model that provides real-time,stroke-order independent handwriting recognition of a user's handwritinginput. In some embodiments, the exemplary user interfaces are userinterfaces of an exemplary handwriting input interface 802 (e.g., shownin FIGS. 8A and 8B), including a handwriting input area 804, a candidatedisplay area 804, and a text input area 808. In some embodiments, theexemplary handwriting input interface 802 also includes a plurality ofcontrol elements 1102, such as a deletion button, a space bar, an Enterbutton, a keyboard switching button, etc. One or more other areas and/orelements may be provided in the handwriting input interface 802 toenable additional functionalities described below.

As described herein, the multi-script handwriting recognition model iscapable of having a very large repertoire of tens of thousands ofcharacters in many different scripts and languages. As a result, it isvery likely that for a handwriting input, the recognition model willidentify a large number of output characters that all have a reasonablygood likelihood of being the character intended by the user. On a userdevice having a limited display area, it is advantageous to provide onlya subset of the recognition results initially, while keeping the otherresults available upon user request.

FIGS. 11A-11G show exemplary user interfaces for displaying a subset ofthe recognition results in a normal view of the candidate display area,along with an affordance for invoking an extended view of the candidatedisplay area for display the remainder of the recognition results. Inaddition, within the extended view of the candidate display area, therecognition results are divided into different categories, and displayedon different tabbed pages in the extended view.

FIG. 11A shows an exemplary handwriting input interface 802. Thehandwriting input interface includes a handwriting input area 804, acandidate display area 806, and a text input area 808. One or morecontrol elements 1102 are also included in the handwriting inputinterface 1002.

As shown in FIG. 11A, the candidate display area 806 optionally includesan area for displaying one or more recognition results and an affordance1104 (e.g., an expansion icon) to invoke an extended version of thecandidate display area 806.

FIGS. 11A-11C illustrate that, as the user provides one or morehandwritten strokes in the handwriting input area 804 (e.g., strokes1106, 1108, and 1110), the user device identifies and displays arespective set of recognition results corresponding to the currentlyaccumulated strokes in the handwriting input area 804. As shown in FIG.11B, after the user has entered a first stroke 1106, the user deviceidentifies and displays three recognition results 1112, 1114, and 1116(e.g., characters “/”, “1”, and “,”). In some embodiments, the smallnumber of candidate characters are displayed in the candidate displayarea 806 in an order according to the recognition confidence associatedwith each character.

In some embodiments, the top-ranked candidate result (e.g., “I”) istentatively displayed in the text input area 808, e.g., within a box1118. The user can optionally confirm that the top-ranked candidate isthe intended input with a simple confirmation input (e.g., by pressingthe “Enter” key, or providing a double-tap gesture in the handwritinginput area).

FIG. 11C illustrates that, before the user has selected any candidaterecognition result, as the user enters two more strokes 1108 and 1110 inthe handwriting input area 804, the additional strokes are rendered inthe handwriting input area 804 with the initial stroke 1106, and thecandidate results are updated to reflect the changes to the recognitionunit(s) identified from the currently accumulated handwriting inputs. Asshown in FIG. 11C, based on the three strokes, the user device hasidentified a single recognition unit. Based on the single recognitionunit, the user device has identified and displayed a number ofrecognition results 1118-1124. In some embodiments, one or more of therecognition results (e.g., 1118 and 1122) currently displayed in thecandidate display area 806 are each a representative candidate characterselected from among multiple similar-looking candidate characters forthe current handwriting input.

As shown in FIGS. 11C-11D, when the user selects the affordance 1104(e.g., using a tap gesture with a contact 1126 over the affordance1104), the candidate display area changes from a normal view (e.g.,shown in FIG. 11C) to an extended view (e.g., shown in FIG. 11D). Insome embodiments, the extended view shows all of the recognition results(e.g., candidate characters) that have been identified for the currenthandwriting input.

In some embodiments, the initially displayed normal view of thecandidate display area 806 only shows the most commonly used charactersused in a respective script or language, while the extended view showsall candidate characters, including characters that are rarely used in ascript or language. The extended view of the candidate display area maybe designed in different ways. FIGS. 11D-11G illustrate an exemplarydesign of the extended candidate display area in accordance with someembodiments.

As shown in FIG. 11D, in some embodiments, the extended candidatedisplay area 1128 includes one or more tabbed pages (e.g., pages 1130,1132, 1134, and 1136) each presenting a respective category of candidatecharacters. The tabbed design shown in FIG. 11D allows the user toquickly find the desired category of characters, and then find thecharacter that he or she intended to enter within the correspondingtabbed page.

In FIG. 11D, the first tabbed page 1130 displays all candidatecharacters that have been identified for the currently accumulatedhandwriting input, including both commonly used characters as well asrare characters. As shown in FIG. 11D, the tabbed page 1130 includes allof the characters shown in the initial candidate display area 806 inFIG. 11C, and a number of additional characters (e.g., “

”, “β”, “

”, etc.) that were not included in the initial candidate display area806.

In some embodiments, the characters displayed in the initial candidatedisplay area 806 include only characters from a set of commonly usedcharacters associated with a script (e.g., all characters in the basicblock of the CJK script, as encoded according to the Unicode standard).In some embodiments, the characters displayed in the extended candidatedisplay area 1128 further include a set of rare characters associatedwith the script (e.g., all characters in the extended block of the CJKscript, as encoded according to the Unicode standard). In someembodiments, the extended candidate display area 1128 further includescandidate characters from other scripts that are not commonly used bythe user, e.g., the Greek script, the Arabic script, and/or the emojiscript.

In some embodiments, as shown in FIG. 11D, the extended candidatedisplay area 1128 includes respective tabbed pages 1130, 1132, 1134, and1138 each corresponding to a respective category of candidate characters(e.g., all characters, rare characters, characters from the Latinscript, and characters from the emoji script, respectively). FIGS.11E-11G illustrate that the user can select each of the different tabbedpages to reveal the candidate characters in a corresponding category.FIG. 11E shows only the rare characters (e.g., characters from theextended block of the CJK script) that correspond to the currenthandwriting input. FIG. 11F shows only Latin and Greek letters thatcorrespond to the current handwriting input. FIG. 11G shows only emojicharacters that correspond to the current handwriting input.

In some embodiments, the extended candidate display area 1128 furtherincludes one or more affordances to sort the candidate characters in arespective tabbed page based on a respective criterion (e.g., based onphonetic spelling, based on number of strokes, and based on radicals,etc.). The ability to sort the candidate characters in each categoryaccording to a criterion other than the recognition confidence scoresprovides the user with additional ability to quickly find the desiredcandidate character for text input.

FIGS. 11H-11K illustrate that, in some embodiments, similar-lookingcandidate characters may be grouped, and only a representative characterfrom each group of similar-looking candidate characters are presented inthe initial candidate display area 806. Since the multi-scriptrecognition model described herein can produce many candidate charactersthat are almost equally good for a given handwriting input, therecognition model cannot always eliminate one candidate at the expenseof another similar-looking candidate. On a device having a limiteddisplay area, displaying many similar-looking candidates all at once isnot helpful for the user to pick out the correct character, because thefine distinction may not be easy to see, and even if the user can seethe desired character, it may be difficult to select it from a verycrammed display using a finger or stylus.

In some embodiments, to address the above issues, the user deviceidentifies candidate characters that have a great resemblance to oneanother (e.g., according to a concordance or dictionary ofsimilar-looking characters, or some image-based criteria), and groupthem into a respective group. In some embodiments, one or more groups ofsimilar-looking characters may be identified from a set of candidatecharacters for a given handwriting input. In some embodiments, the userdevice identified a representative candidate character from among aplurality of similar-looking candidate characters in the same group, andonly displays the representative candidate in the initial candidatedisplay area 806. If a commonly used character does not look similarenough to any other candidate characters, it is displayed by itself. Insome embodiments, as shown in FIG. 11H, the representative candidatecharacter (e.g., candidate characters 1118 and 1122, “

” and “T”) of each group is displayed in a different manner (e.g., in abolded box) from a candidate character (e.g., candidate characters 1120and 1124, “

” and “J”) that does not belong to any group. In some embodiments, thecriterion for choosing the representative character of a group is basedon a relative usage frequency of the candidate characters in the group.In some embodiments, other criteria may be used.

In some embodiments, once the representative character(s) are displayedto the user, the user can optionally expand the candidate display area806 to show the similar-looking candidate characters in an expandedview. In some embodiments, the selection of a particular representativecharacter can cause the expanded view of only those candidate charactersin the same group as the selected representative character.

Various designs for providing the expanded view of the similar-lookingcandidates are possible. FIGS. 11H-11K illustrate one embodiment inwhich the expanded view of a representative candidate character isinvoked by a predetermined gesture (e.g., an expand gesture) detectedover a representative candidate character (e.g., representativecharacter 1118). The predetermined gesture (e.g., an expand gesture) forinvoking an expanded view is different from the predetermined gesture(e.g., a tap gesture) for selecting the representative character fortext input.

As shown in FIGS. 11H-11I, when the user provides an expand gesture(e.g., as indicated by two contacts 1138 and 1140 moving away from eachother) over the first representative character 1118, the area displayingthe representative character 1118 is expanded, and three similar-lookingcandidate characters (e.g., “

”, “

” and “

”) are presented in an enlarged view (e.g., in enlarged boxes 1142,1144, and 1146, respectively) as compared to the other candidatecharacters (e.g., “

”) which are not in the same expanded group.

As shown in FIG. 11I, when presented in the enlarged view, finedistinctions of the three similar-looking candidate characters (e.g., “

”, “

” and “

”) can be more easily seen by the user. If one of the three candidatecharacters is the intended character input, the user can select thecandidate character, e.g., by touching the area in which the characteris displayed. As shown in FIGS. 11J-11K, the user has selected (withcontact 1148) the second character (e.g., “

”) shown in box 1144 in the expanded view. In response, the selectedcharacter (e.g., “

”) is entered into the text input area 808 at the insertion pointindicated by the cursor. As shown in FIG. 11K, once a character has beenselected, the handwriting input in the handwriting input area 804 andthe candidate characters in the candidate display area 806 (or theextended view of the candidate display area) are cleared for subsequenthandwriting input.

In some embodiments, if the user does not see a desired candidatecharacter in the expanded view of the first representative candidatecharacter 1142, the user can optionally use the same gesture to expandother representative characters displayed in the candidate display area806. In some embodiments, expanding another representative character inthe candidate display area 806 automatically restores the currentlypresented expanded view to a normal view. In some embodiments, the useroptionally uses a contraction gesture to restore the currently expandedview to a normal view. In some embodiments, the user can scroll thecandidate display area 806 (e.g., to the left or to the right) to revealother candidate characters that are not visible in the candidate displayarea 806.

FIGS. 12A-12B are flow charts of an exemplary process 1200 in which afirst subset of recognition results are presented in an initialcandidate display area, while a second subset of recognition results arepresented in an extended candidate display area that is hidden from viewuntil specifically invoked by a user. In the exemplary process 1200, thedevice identifies from a plurality of handwriting recognition resultsfor a handwriting input, a subset of recognition results that have avisual similarity level exceeding a predetermined threshold. The userdevice then selects a representative recognition result from the subsetof recognition results, and displays the selected representativerecognition result in a candidate display area of the display. Theprocess 1200 is illustrated in FIGS. 11A-11K.

As shown in FIG. 12A, in the example process 1200, the user devicereceives (1202) a handwriting input from a user. The handwriting inputincludes one or more handwritten strokes (e.g., 1106, 1108, 1110 in FIG.11C) provided in a handwriting input area (e.g., 806 in FIG. 11C) of ahandwriting input interface (e.g., 802 in FIG. 11C). The user device,based on a handwriting recognition model, identifies (1204) a pluralityof output characters (e.g., characters shown in tabbed page 1130, FIG.11C) for the handwriting input. The user device divides (1206) theplurality of output characters into two or more categories based on apredetermined categorization criterion. In some embodiments, thepredetermined categorization criterion determines (1208) whether arespective character is a commonly used character or a rare character.

In some embodiments, the user device displays (1210), in an initial viewof a candidate display area (e.g., 806 as shown in FIG. 11C) of thehandwriting input interface, respective output characters in a firstcategory (e.g., commonly used characters) of the two or more categories,wherein the initial view of the candidate display area is concurrentlyprovided with an affordance (e.g., 1104 in FIG. 11C) for invoking anextended view of the candidate display area (e.g., 1128 in FIG. 11D).

In some embodiments, the user device receives (1212) a user inputselecting the affordance for invoking the extended view, e.g., as shownin FIG. 11C. In response to the user input, the user device displays(1214), in the extended view of the candidate display area, therespective output characters in the first category and respective outputcharacters in at least a second category of the two or more categorieswhich were not previously displayed in the initial view of the candidatedisplay area, e.g., as shown in FIG. 11D.

In some embodiments, the respective characters in the first category arecharacters found in a dictionary of commonly used characters, andrespective characters in the second category are characters found in adictionary of rare characters. In some embodiments, the dictionary ofcommonly used characters and the dictionary of rare characters aredynamically adjusted or updated based on a usage history associated withthe user device.

In some embodiments, the user device identifies (1216) from theplurality of output characters, a group of characters that are visuallysimilar to one another in accordance with a predetermined similaritycriterion (e.g., based on a dictionary of similar characters or based onsome spatially-derived features). In some embodiments, the user deviceselects from the group of visually similar characters a representativecharacter based on a predetermined selection criterion (e.g., based onhistoric usage frequency). In some embodiments, the predeterminedselection criterion is based on a relative usage frequency of thecharacters in the group. In some embodiments, the predeterminedselection criterion is based on a preferred input language associatedwith the device. In some embodiments, the representative candidate isselected based on other factors indicative of the likelihood that eachcandidate is the intended input by the user. These factors include, forexample, whether the candidate character belongs to a script for a softkeyboard that is currently installed on the user's device, or whetherthe candidate character is among a set of most commonly used charactersin a particular language associated with the user or user device, etc.

In some embodiments, the user device displays (1220) the representativecharacter (e.g., “

”) in the initial view of the candidate display area (e.g., 806 in FIG.11H) in lieu of other characters (e.g., “

”, “

” in the group of visually similar characters. In some embodiments,visual indications (e.g., selective visual highlighting, specialbackground) is provided in the initial view of the candidate displayarea to indicate whether each candidate character is a representativecharacter of a group or a normal candidate character not within anygroup. In some embodiments, the user device receives (1222), from theuser, a predetermined expansion input (e.g., an expand gesture) directedto the representative character displayed in the initial view of thecandidate display area, e.g., as shown in FIG. 11H. In some embodiments,in response to the receipt of the predetermined expansion input, theuser device concurrently displays (1224) a magnified view of therepresentative character and respective magnified view of one or moreother characters in the group of visually similar characters, e.g., asshown in FIG. 11I.

In some embodiments, the predetermined expansion input is an expandgesture detected over the representative character displayed in thecandidate display area. In some embodiments, the predetermined expansioninput is a contact that is detected over the representative characterdisplayed in the candidate display area and that is sustained for longerthan a predetermined threshold time. In some embodiments, the sustainedcontact for expanding the group has a longer threshold duration than atap gesture of selecting the representative character for text input.

In some embodiments, each representative character is displayedconcurrently with a respective affordance (e.g., a respective expandbutton) to invoke the extended view of its group of similar-lookingcandidate characters. In some embodiments, the predetermined expansioninput is a selection of the respective affordance associated with therepresentative character.

As described herein, in some embodiments, the repertoire of themulti-script handwriting recognition model includes an emoji script. Thehandwriting input recognition module can recognizes an emoji characterbased on a user's handwriting input. In some embodiments, thehandwriting recognition module presents both emoji characters identifieddirectly from the handwriting, and a character or word in a naturalhuman language representing the identified emoji character. In someembodiments, the handwriting input module recognizes a character or wordin a natural human language based on a user's handwriting input, andpresents both the recognized character or word, and an emoji characterthat corresponds to the recognized character or word. In other words,the handwriting input module provides ways for entering an emojicharacter without switching from the handwriting input interface to anemoji keyboard. In addition, the handwriting input module also providesa way to enter regular natural language characters and words, by drawingan emoji character by hand. FIGS. 13A-13E provide exemplary userinterfaces illustrating these different ways of entering emojicharacters and regular natural language characters.

FIG. 13A shows an exemplary handwriting input interface 802 invokedunder a chat application. The handwriting input interface 802 includes ahandwriting input area 804, a candidate display area 806, and a textinput area 808. In some embodiments, once the user is satisfied with thetext composition in the text input area 808, the user can choose to sendthe text composition to another participant of the current chat session.The dialog history of the chat session is shown in the dialogue panel1302. In this example, the user has received a chat message 1304 (e.g.,“Happy Birthday

”) which is displayed in the dialogue panel 1302.

As shown in FIG. 13B, the user has provided a handwriting input 1306 forthe English word “Thanks” in a handwriting input area 804. In responseto the handwriting input 1306, the user device has identified a numberof candidate recognition results (e.g., recognition results 1308, 1310,and 1312). The top-ranked recognition result 1303 has been tentativelyentered into the text input area 808 within a box 1314.

As shown in FIG. 13C, after the user has entered the handwritten word“Thanks” in the handwriting input area 806, the user then draws astylized exclamation point with strokes 1316 (e.g., an elongated circlewith a round circle underneath) in the handwriting input area 806. Theuser device recognizes that the additional strokes 1316 form a separaterecognition unit from the other recognition units previously recognizedfrom the accumulated handwritten strokes 1306 in the handwriting inputarea 806. Based on the newly entered recognition unit (i.e., therecognition unit formed by the strokes 1316), the user device identifiesan emoji character (e.g., a stylized “!”) using the handwritingrecognition model. Based on this recognized emoji character, the userdevice presents a first recognition result 1318 (e.g., “Thanks!” withthe stylized “!”) in the candidate display area 806. In addition, theuser device also identifies a number “8” which also visually resemblesthe newly entered recognition unit. Based on this recognized digit, theuser device presents a second recognition result 1322 (e.g., “Thanks 8”)in the candidate display area 806. In addition, based on the identifiedemoji character (e.g., the stylized “!”), the user device alsoidentifies a regular character (e.g., a regular character“!”)corresponding to the emoji character. Based on this indirectlyidentified regular character, the user device presents a thirdrecognition result 1320 (e.g., “Thanks!” with the regular“!”) in thecandidate display area 806. At this point, the user may select any oneof the candidate recognition results 1318, 1320, and 1322 to enter itinto the text input area 808.

As shown in FIG. 13D, the user continues to provide additionalhandwritten strokes 1324 in the handwriting input area 806. This time,the user has drawn a heart symbol following the stylized exclamationpoint. In response to the new handwritten strokes 1324, the user devicerecognizes that the newly provided handwritten strokes 1324 form yetanother new recognition unit. Based on the new recognition unit, theuser device identifies the emoji character “♡” and, alternatively, thedigit “0” as the candidate characters for the new recognition unit.Based on these new candidate characters recognized from the newrecognition unit, the user device presents two updated candidaterecognition results 1326 and 1330 (e.g., “Thanks

♡ v” and “Thanks 80”). In some embodiments, the user device furtheridentifies the regular character(s) or word(s) (e.g., “Love”) thatcorrespond to the identified emoji character (e.g., “♡”). Based on theidentified regular character(s) or word(s) for the recognized emojicharacter, the user device presents a third recognition result 1328 inwhich the recognized emoji character(s) are replaced with thecorresponding regular character(s) or word(s). As shown in FIG. 13D, inthe recognition result 1328, the emoji character “

” is replaced with a normal exclamation point “!”, and the emojicharacter “p” has been replaced with regular characters or word “Love”.

As shown in FIG. 13E, the user has selected one of the candidaterecognition results (e.g., candidate result 1326 showing themixed-script text “Thanks

♡”), and text of the selected recognition result is entered into thetext input area 808, and subsequently sent to the other participant ofthe chat session. The message bubble 1332 shows the text of the messagein the dialogue panel 1302.

FIG. 14 is a flow chart of an exemplary process 1400 in which the userenters an emoji character using a handwriting input. FIGS. 13A-13Eillustrates the exemplary process 1400 in accordance with someembodiments.

In the process 1400, the user device receives (1402) a handwriting inputfrom a user. The handwriting input includes a plurality of handwrittenstrokes provided in an handwriting input area of a handwriting inputinterface. In some embodiments, the user device recognizes (1404), basedon a handwriting recognition model, a plurality of output charactersfrom the handwriting input. In some embodiments, the output charactersinclude at least a first emoji character (e.g., the stylized exclamationpoint “

” or the emoji character “♡” in FIG. 13D) and at least a first character(e.g., a character from the word “Thanks” in FIG. 13D) from a script ofa natural human language. In some embodiments, the user device displays(1406) a recognition result (e.g., result 1326 in FIG. 13D) comprisingthe first emoji character (e.g., the stylized exclamation point

” or the emoji character “♡” in FIG. 13D) and the first character (e.g.,a character from the word “Thanks” in FIG. 13D) from the script of thenatural human language in a candidate display area of the handwritinginput interface, e.g., as shown in FIG. 13D.

In some embodiments, based on the handwriting recognition model, theuser device optionally recognizes (1408) at least a first semantic unit(e.g., the word “thanks”) from the handwriting input, wherein the firstsemantic unit comprises a respective character, word or phrase that iscapable of conveying a respective semantic meaning in a respective humanlanguage. In some embodiments, the user device identifies (1410) asecond emoji character (e.g., a “handshake” emoji character) associatedwith the first semantic unit (e.g., the word “Thanks”) recognized fromthe handwriting input. In some embodiments, the user device displays(1412), in the candidate display area of the handwriting inputinterface, a second recognition result (e.g., a recognition resultshowing a “handshake” emoji character followed by the “

” and a “♡” emoji characters) comprising at least the second emojicharacter identified from the first semantic unit (e.g., the word“Thanks”). In some embodiments, displaying the second recognition resultfurther includes concurrently displaying the second recognition resultwith a third recognition result (e.g., a recognition result “Thanks

♡”) comprising at least the first semantic unit (e.g., the word“Thanks”).

In some embodiments, the user receives a user input selecting the firstrecognition result displayed in the candidate display area. In someembodiments, in response to the user input, the user device enters textof the selected first recognition result in a text input area of thehandwriting input interface, where the text includes at least the firstemoji character and the first character from the script of the naturalhuman language. In other words, the user is able to enter a mixed-scripttext input using a single handwriting input (albeit, a handwriting inputcomprising multiple strokes) in the handwriting input area, withoutswitching between a natural language keyboard and an emoji characterkeyboard.

In some embodiments, the handwriting recognition model has been trainedon a multi-script training corpus comprising writing samplescorresponding to characters of at least three non-overlapping scripts,and the three non-overlapping scripts includes a set of emojicharacters, Chinese characters, and Latin script.

In some embodiments, the user device identifies (1414) a second semanticunit (e.g., the word “Love”) corresponding to the first emoji character(e.g., the “♡” emoji character) recognized directly from the handwritinginput. In some embodiments, the user device displays (1416) in thecandidate display area of the handwriting input interface, a fourthrecognition result (e.g., 1328 in FIG. 13D) comprising at least thesecond semantic unit (e.g., the word “Love”) identified from the firstemoji character (e.g., the “♡” emoji character). In some embodiments,the user device concurrently displays the fourth recognition result(e.g., result 1328 “Thanks! Love”) with the first recognition result(e.g., result “Thank♡

”) in the candidate display area, as shown in FIG. 13D.

In some embodiments, the user device allows the user to enter regulartext by drawing an emoji character. For example, if the user does notknow how to spell the word “elephant,” the user optionally draw astylized emoji character for “elephant” in the handwriting input area,and if the user device can correctly recognize the handwriting input asan emoji character for “elephant,” the user device optionally alsopresents the word “elephant” in normal text as one of the recognitionresults displayed in the candidate display area. In another example, theuser may draw a stylized cat in the handwriting input area, in lieu ofwriting the Chinese character “

”. If the user device identifies the emoji character for “cat” based onthe handwriting input provided by the user, the user device optionallyalso presents the Chinese character “

” which means “cat” in Chinese, along with the emoji character for “cat”in the candidate recognition results. By presenting normal text for arecognized emoji character, the user device provides an alternative wayof entering complex characters or words using a few stylized strokescommonly associated with a well-known emoji character. In someembodiments, the user device stores a dictionary linking emojicharacters with their corresponding normal text (e.g., characters,words, phrases, symbols, etc.) in one or more preferred scripts orlanguages (e.g., English or Chinese).

In some embodiments, the user device recognizes an emoji character basedon a visual resemblance of the emoji character to an image generatedfrom the handwriting input. In some embodiments, to enable therecognition of emoji characters from a handwriting input, thehandwriting recognition model used on the user device is trained using atraining corpus that include both handwriting samples corresponding tocharacters of a script of a natural human language and also handwritingsamples corresponding to a set of artificially designed emojicharacters. In some embodiments, the emoji characters related to thesame semantic concept may have different appearance when used in a mixedinput with text of different natural languages. For example, an emojicharacter for the semantic concept of “Love” may be a “heart” emojicharacter when presented with normal text of one natural language (e.g.,Japanese), and a “kiss” emoji character when presented with normal textof another natural language (e.g., English or French).

As described herein, when performing recognition of a multi-characterhandwriting input, the handwriting input module performs segmentation ofthe handwriting input currently accumulated in the handwriting inputarea, and divides the accumulated strokes into one or more recognitionunits. One of the parameters used to determine how to segment ahandwriting input may be how the strokes are clustered in thehandwriting input area and the distance between the different clustersof strokes. Since people have different writing styles. Some people tendto write very sparsely with large distances between strokes or differentparts of the same character, while other people tend to write verydensely with very small distances between strokes or differentcharacters. Even for the same user, due to imperfect planning, ahandwritten character may depart from a balanced appearance and belopsided, stretched, or squeezed in different ways. As described herein,the multi-script handwriting recognition model provides stroke-orderindependent recognition, therefore, the user may write characters orparts of characters out of sequence. As a result, spatial uniformity andbalance in a handwriting input between characters may be difficult toattain.

In some embodiments, the handwriting input model described hereinprovides a way for the user to inform the handwriting input modulewhether to merge two adjacent recognition units into a singlerecognition unit or to divide a single recognition unit into twoseparate recognition units. With the user's help, the handwriting inputmodule can revise the initial segmentation, and generate a resultintended by the user.

FIGS. 15A-15J illustrate some exemplary user interfaces and processes inwhich the user provides a predetermined pinch and expand gestures tomodify the recognition units identified by the user device.

As shown in FIGS. 15A-15B, a user has entered a plurality of handwrittenstrokes 1502 (e.g., three strokes) in the handwriting input area 806 ofa handwriting input interface 802. The user device has identified asingle recognition unit based on the currently accumulated handwrittenstrokes 1502, and presented three candidate characters 1504, 1506, and1508 (e.g., “

”, “

”, and “

”, respectively) in the candidate display area 806.

FIG. 15C shows that the user has further entered a few additionalstrokes 1510 to the right of the initial handwritten strokes 1502 in thehandwriting input area 606. The user device determines (e.g., based onthe dimensions and spatial distributions of the plurality of strokes1502 and 1510) that the strokes 1502 and the strokes 1510 should beconsidered as two separate recognition units. Based on the division ofthe recognition units, the user device provides the input images of thefirst and second recognition units to the handwriting recognition modeland obtains two sets of candidate characters. The user device thengenerates a plurality of recognition results (e.g., 1512, 1514, 1516,and 1518) based on different combinations of the recognized characters.Each recognition result includes a recognized character for the firstrecognition unit, and a recognized character for the second recognitionunit. As shown in FIG. 15C, the plurality of recognition results 1512,1514, 1516, and 1518 each include two recognized characters.

In this example, suppose that the user in fact intended the handwritinginput to be recognized as a single character, but unintentionally lefttoo much space between the left portion (e.g., the left radical “

”) and the right portion (e.g., the right radical “

”) of the handwritten character (e.g., “

”). Having seen the results (e.g., 1512, 1514, 1516, and 1518) presentedin the candidate display area 806, the user would realize that the userdevice has incorrectly segmented the current handwriting input into tworecognition units. Although the segmentation may be based on anobjective standard, it would not be desirable for the user to delete thecurrent handwriting input and rewrite the whole character again with asmaller distance between the left and the right portions.

Instead, as shown in FIG. 15D, the user uses a pinch gesture over thetwo clusters of the handwritten strokes 1502 and 1510 to indicate to thehandwriting input module that the two recognition units identified bythe handwriting input module should be merged as a single recognitionunit. The pinch gesture is indicated by two contacts 1520 and 1522 onthe touch-sensitive surface that are move toward each other.

FIG. 15E shows that, in response to the user's pinch gesture, the userdevice has revised the segmentation of the currently accumulatedhandwriting input (e.g., strokes 1502 and 1510), and merged thehandwritten strokes into a single recognition unit. As shown in FIG.15E, the user device has provided the input image based on the revisedrecognition unit to the handwriting recognition model, and obtainedthree new candidate characters 1524, 1526, and 1528 (e.g., “

”, “

”, and “

”) for the revised recognition unit. In some embodiments, as shown inFIG. 15E, the user device optionally adjusts the rendering of thehandwriting input within the handwriting input area 806, such that thedistance between the left cluster and the right cluster of thehandwritten strokes is reduced. In some embodiments, the user devicedoes not alter the rendering of the handwriting input shown in thehandwriting input area 608 in response to the pinch gesture. In someembodiments, the user device distinguishes the pinch gesture from aninput stroke based on the two simultaneous contacts (as opposed to onesingle contact) detected in the handwriting input area 806.

As shown in FIG. 15F, the user has entered two more strokes 1530 to theright of the previously entered handwriting input (i.e., the strokes forthe character “

”). The user device determines that the newly entered strokes 1530 is anew recognition unit, and recognizes a candidate character (e.g., “

”) for the newly identified recognition unit. The user device thencombines the newly identified character (e.g., “

”) with the candidate characters for the earlier identified recognitionunit, and presents a number of different recognition results (e.g.,results 1532 and 1534) in the candidate display area 806.

Following the handwritten strokes 1530, the user continues to write morestrokes 1536 (e.g., three more strokes) to the right of the strokes1530, as shown in FIG. 15G. Since the horizontal distance between thestrokes 1530 and the strokes 1536 is very small, the user devicedetermines that the strokes 1530 and the strokes 1536 belong to the samerecognition unit, and provides an input image formed by the strokes 1530and 1536 to the handwriting recognition model. The handwritingrecognition model identifies three different candidate characters forthe revised recognition unit, and generates two revised recognitionresults 1538 and 1540 for the currently accumulated handwriting input.

In this example, suppose that the last two sets of strokes 1530 and 1536are in fact intended as two separate characters (e.g., “

” and “±”). After the user sees that the user device has incorrectlycombined the two sets of strokes 1530 and 1536 into a single recognitionunit, the user proceeds to provide an expand gesture to notify the userdevice that the two sets of strokes 1530 and 1536 should be divided intotwo separate recognition units. As shown in FIG. 15H, the user makes twocontacts 1542 and 1544 around the stroke 1530 and 1536, and then movesthe two contacts away from each other in a generally horizontaldirection (i.e., along the default writing direction).

FIG. 15I shows that, in response to the user's expand gesture, the userdevice revised the previous segmentation of the currently accumulatedhandwriting input, and assigned the strokes 1530 and the strokes 1536into two consecutive recognition units. Based on the input imagesgenerated for the two separate recognition units, the user deviceidentifies one or more candidate characters for the first recognitionunit based on the strokes 1530, and one or more candidate characters forthe second recognition unit based on the strokes 1536. The user devicethen generates two new recognition results 1546 and 1548 based ondifferent combinations of the recognized characters. In someembodiments, the user device optionally modifies the rendering of thestrokes 1536 and 1536 to reflect the division of the previouslyidentified recognition unit.

As shown in FIGS. 15J-15K, the user has selected (as indicated by thecontact 1550) one of the candidate recognition results displayed in thecandidate display area 806, and the selected recognition result (e.g.,result 1548) has been entered in the text input area 808 of the userinterface. After the selected recognition result has been entered intothe text input area 808, the candidate display area 806 and thehandwriting input area 804 are both cleared and ready to displaysubsequent user input.

FIGS. 16A-16B are flow charts of an exemplary process 1600 in which theuser uses predetermined gesture (e.g., a pinch gesture and/or an expandgesture) to notify the handwriting input module how to segment or revisean existing segmentation of the current handwriting input. FIGS. 15J and15K provide an illustration of the exemplary process 1600 in accordancewith some embodiments.

In some embodiments, the user device receives (1602) a handwriting inputfrom a user. The handwriting input includes a plurality of handwrittenstrokes provided in a touch-sensitive surface coupled to the device. Insome embodiments, the user device renders (1604), in real-time, theplurality of handwritten strokes in a handwriting input area (e.g.,handwriting input area 806 of FIGS. 15A-15K) of a handwriting inputinterface. The user device receiving one of a pinch gesture input and aexpand gesture input over the plurality of handwritten strokes, e.g., asshown in FIGS. 15D and 15H.

In some embodiments, upon receiving a pinch gesture input, the userdevice generates (1606) a first recognition result based on theplurality of handwritten strokes by treating the plurality ofhandwritten strokes as a single recognition unit, e.g., as illustratedin FIGS. 15C-15E.

In some embodiments, upon receiving a expand gesture input, the userdevice generates (1608) a second recognition result based on theplurality of handwritten strokes by treating the plurality ofhandwritten strokes as two separate recognition units pulled apart bythe expand gesture input, e.g., as illustrated in FIGS. 15G-15I.

In some embodiments, upon generating a respective one of the first andsecond recognition results, the user device displays the generatedrecognition result in a candidate display area of the handwriting inputinterface, e.g., as shown in FIGS. 15E, and 15I.

In some embodiments, the pinch gesture input comprises two simultaneouscontacts on the touch-sensitive surface that converge toward each otherin an area occupied by the plurality of handwritten strokes. In someembodiments, the expand gesture input comprises two simultaneouscontacts on the touch-sensitive surface that diverge from each other inan area occupied by the plurality of handwritten strokes.

In some embodiments, the user device identifies (e.g., 1614) twoadjacent recognition units from the plurality of handwritten strokes.The user device displays (1616), in the candidate display area, aninitial recognition result (e.g., results 1512, 1514, 1516, and 1518 inFIG. 15C) comprising respective characters recognized from the twoadjacent recognition units, e.g., as illustrated in FIG. 15C. In someembodiments, when displaying the first recognition result (e.g., result1524, 1526, or 1528 in FIG. 15E) in response to a pinch gesture, theuser device replaces (1618) the initial recognition result with thefirst recognition result in the candidate display area. In someembodiments, the user device receives (1620) the pinch gesture inputwhile the initial recognition result is displayed in the candidatedisplay area, as shown in FIG. 15D. In some embodiments, in response tothe pinch gesture input, the user device re-renders (1622) the pluralityof handwritten strokes to reduce a distance between the two adjacentrecognition units in the handwriting input area, e.g., as shown in FIG.15E.

In some embodiments, the user device identifies (1624) a singlerecognition unit from the plurality of handwritten strokes. The userdevice displays (1626), in the candidate display area, an initialrecognition result (e.g., result 1538 or 1540 of FIG. 15G) comprising acharacter (e.g., “

” “

” recognized from the single recognition unit. In some embodiments, whendisplaying the second recognition result (e.g., result 1546 or 1548 inFIG. 15I) in response to the expand gesture, the user device replaces(1628) the initial recognition result (e.g., results 1538 or 1540) withthe second recognition result (e.g., result 1546 or 1548) in thecandidate display area, e.g., as illustrated in FIGS. 15H-151. In someembodiments, the user device receives (1630) the expand gesture inputwhile the initial recognition result is displayed in the candidatedisplay area, as illustrated in FIG. 15H. In some embodiments, inresponse to the expand gesture input, the user device re-renders (1632)the plurality of handwritten strokes to increase a distance between afirst subset of strokes assigned to a first recognition unit and asecond subset of handwritten strokes assigned to a second recognitionunit in the handwriting input area, as illustrated in FIGS. 15H and 15I.

In some embodiments, the user optionally provides a pinch gesture toinform the user device to treat a plurality of strokes as a singlerecognition unit, immediately after the user has provided the strokesand realized that the strokes may be too spread out for a correctsegmentation based on a standard segmentation process. The user devicecan distinguish the pinch gesture from a regular stroke based on the twosimultaneous contacts present in a pinch gesture. Similarly, in someembodiments, the user optionally provides an expand gesture to informthe user device to treat a plurality of strokes two separate recognitionunits, immediately after the user has provided the strokes and realizedthat the strokes may be too close together for a correct segmentationbased on a standard segmentation process. The user device candistinguish the expand gesture from a regular stroke based on the twosimultaneous contacts present in a pinch gesture.

In some embodiments, the motion direction of the pinch or expand gestureis optionally used to provide additional guidance on how to segment thestrokes under the gesture. For example, if multi-line handwriting inputis enabled for the handwriting input area, a pinch gesture with twocontacts moving in the vertical direction can inform the handwritinginput module to merge two recognition units identified in two adjacentlines into a single recognition unit (e.g., as a top radical and abottom radical). Similarly, an expand gesture with two contacts movingin the vertical direction can inform the handwriting input module todivide a single recognition unit into two recognition units in twoadjacent lines. In some embodiments, the pinch and expand gestures canalso provide segmentation guidance in a sub-portion of a characterinput, e.g., merging two sub-components or divide a single component ina composite character (

,

,

,

,

, etc.), in different parts (e.g., upper, lower, left, or rightportions) of the composite character. This is particularly helpful forrecognizing complex composite Chinese characters, because users tends tolose the correct proportions and balance when writing a complexcomposite character by hand. Being able to adjust the proportions andbalance of the handwriting input, e.g., by way of the pinch and expandgestures, after the completion of the handwriting input is particularhelpful for the user to input the correct character without having tomake several attempts to get at the correct proportions and balance.

As described herein, the handwriting input module allows a user to entera multi-character handwriting input, and allows out-of-order strokes forthe multi-character handwriting input within a character, acrossmultiple characters, and even across multiple phrases, sentences, and/orlines in the handwriting input area. In some embodiments, thehandwriting input module also provides character-by-character deletionin the handwriting input area, where the order of character deletion isin the reverse writing direction, and independent of when the strokesfor each character has been provided in the handwriting input area. Insome embodiments, the deletion of each recognition unit (e.g., characteror radical) in the handwriting input area is optionally performedstroke-by-stroke, where the strokes are deleted in a reverse temporalorder by which they were provided within the recognition unit. FIGS.17A-17H illustrate exemplary user interfaces for responding to adeletion input from a user and provide character-by-character deletionin a multi-character handwriting input.

As shown in FIG. 17A, the user has provided a plurality of handwrittenstrokes 1702 in the handwriting input area 804 of the handwriting inputuser interface 802. Based on the currently accumulated strokes 1702, theuser device presents three recognition results (e.g., results 1704,1706, and 1708) in the candidate display area 806. As shown in FIG. 17B,the user has provided an additional plurality of strokes 1710 in thehandwriting input area 806. The user device recognizes three new outputcharacters, and replaces the three previous recognition results 1704,1706, and 1708 with the three new recognition results 1712, 1714, and1716. In some embodiments, as shown in FIG. 17B, even though the userdevice has identified two separate recognition units from the currenthandwriting input (e.g., strokes 1702 and strokes 1710), the cluster ofstrokes 1710 does not correspond well to any known characters in therepertoire of the handwriting recognition module. As a result, thecandidate characters (e.g., “

” “

”) identified for the recognition unit comprising strokes 1710 are allhave a recognition confidence below a predetermined threshold. In someembodiments, the user device presents a partial recognition result(e.g., result 1712) which includes only a candidate character (e.g., “

”) for the first recognition unit, but not any candidate character forthe second recognition unit in the candidate display area 806. In someembodiments, the user device further displays a full recognition result(e.g., result 1714 or 1716) which includes a candidate character forboth recognition units, regardless of whether the recognition confidencehas passed the predetermined threshold. Providing a partial recognitionresult informs the user which part of the handwritten input needsrevision. In addition, the user can also choose to enter the correctlyrecognized portion of handwriting input first, and then rewrite theportion that was not correctly recognized.

FIG. 17C shows that the user has continued to provide an additionalhandwritten stroke 1718 to the left of strokes 1710. Based on therelative location and distance of the stroke 1718, the user devicedetermines that the newly added stroke belong to the same recognitionunit as the cluster of handwritten strokes 1702. Based on the revisedrecognition units recognizes a new character (e.g., “

”) for the first recognition unit, and generates a set of newrecognition results 1720, 1722, and 1724. Again, the first recognitionresult 1720 is a partial recognition result, because none of thecandidate characters identified for the strokes 1710 meet thepredetermined confidence threshold.

FIG. 17D shows that the user has now entered a plurality of new strokes1726 to between the strokes 1702 and the strokes 1710. The user deviceassigns the newly entered strokes 1726 to the same recognition unit asthe strokes 1710. Now, the user has completed entering all of thehandwritten strokes for the two Chinese characters (e.g., “

”), and the correct recognition result 1728 is shown in the candidatedisplay area 806.

FIG. 27E shows that the user has entered an initial portion of adeletion input, e.g., by making a light contact 1730 on the deletebutton 1732. If the user maintains the contact with the delete button1732, the user can delete the current handwriting inputcharacter-by-character (or recognition unit by recognition unit). Thedeletion is not performed for all of the handwritten input at the sametime.

In some embodiments, when the user's finger first touches the deletebutton 1732 on the touch-sensitive screen, the last recognition unit(e.g., the recognition unit for the character “

”) in the default writing direction (e.g., from left to right) isvisually highlighted (e.g., highlighted with a border 1734, or lightenedbackground, etc.) relative to the other recognition unit(s) concurrentlydisplayed within the handwriting input area 804, as shown in FIG. 17E.

In some embodiments, when the user device detects that the user hasmaintained the contact 1730 on the delete button 1732 for more than athreshold duration, the user device removes the highlighted recognitionunit (e.g., in box 1734) from the handwriting input area 806, as shownin FIG. 17F. In addition, the user device also revises the recognitionresults shown in the candidate display area 608 to delete any outputcharacters generated based on the deleted recognition unit, as shown inFIG. 17F.

FIG. 17F further illustrates that, if the user continues to maintain thecontact 1730 on the delete button 1732 after the last recognition unit(e.g., the recognition unit for the character “

”) in the handwriting input area 806 has been deleted, the adjacentrecognition unit (e.g., the recognition unit for the character “

”) to the deleted recognition unit becomes the next recognition unit tobe deleted. As shown in FIG. 17F, the remaining recognition unit hasbecome visually highlighted (e.g., in a box 1736), and ready to bedeleted. In some embodiments, the visual highlighting of the recognitionunit provides a preview of the recognition unit that would be deleted ifthe user continues to maintain the contact with the delete button. Ifthe user breaks the contact with the delete button before the thresholdduration is reached, the visual highlighting is removed from the lastrecognition unit, and the recognition unit is not deleted. As a personskilled in the art would recognize, the duration of contact is reseteach time a recognition unit has been deleted. In addition, in someembodiments, the contact intensity (e.g., the pressure by which the userhas applied the contact 1730 with the touch-sensitive screen) isoptionally used to adjust the threshold duration to confirm the user'sintent to delete the currently highlighted recognition unit. FIGS. 17Fand 17G illustrate that the user has broken the contact 1730 on thedelete button 1732 before the threshold duration is reached, and therecognition unit for the character “

” is preserved in the handwriting input area 806. When the user hasselected (e.g., as indicated by the contact 1740) the first recognitionresult (e.g., result 1738) for the recognition unit, and the text in thefirst recognition result 1738 is entered into the text input area 808,as shown in FIGS. 17G-17H.

FIGS. 18A-18B are flow charts of an exemplary process 1800 in which theuser device provides character-by-character deletion in amulti-character handwriting input. In some embodiments, the deletion ofthe handwriting input is performed before the characters recognized fromthe handwriting input have been confirmed and entered into the textinput area of the user interface. In some embodiments, the deletion ofthe characters in the handwriting input proceeds according to thereverse spatial order of the recognition units identified from thehandwriting input, and is independent of the temporal sequence by whichthe recognition units are formed. FIGS. 17A-17H illustrate the exemplaryprocess 1800 in accordance with some embodiments.

As shown in FIG. 18A, in the exemplary process 1800, the user devicereceives (1802) a handwriting input from a user, the handwriting inputincluding a plurality of handwritten strokes provided in an handwritinginput area (e.g., area 804 in FIG. 17D) of a handwriting inputinterface. The user device identifies (1804) a plurality of recognitionunits from the plurality of handwritten strokes, each recognition unitincluding a respective subset of the plurality of handwriting strokes.For example, as shown in FIG. 17D, the first recognition unit includesstrokes 1702 and 1718, and the second recognition unit includes strokes1710 and 1726. The user device generates (1806) a multi-characterrecognition result (e.g., result 1728 in FIG. 17D) comprising respectivecharacters recognized from the plurality of recognition units. In someembodiments, the user device displays the multi-character recognitionresult (e.g., result 1728 in FIG. 17D) in a candidate display area ofthe handwriting input interface. In some embodiments, while themulti-character recognition result is displayed in the candidate displayarea, the user device receives (1810) a deletion input (e.g., contact1730 on delete button 1732) from the user, e.g., as shown in FIG. 17E.In some embodiments, in response to receiving the deletion input, theuser device removes (1812) an end character (e.g., the character “

” that appear at the end of the spatial sequence “

”) from the multi-character recognition result (e.g., result 1728)displayed in the candidate display area (e.g., candidate display area806), e.g., as illustrated in FIGS. 17E-17F.

In some embodiments, the user device renders (1814) the plurality ofhandwritten strokes in the handwriting input area of the handwritinginput interface as the plurality of handwritten strokes are provided bythe user in real-time, e.g., as illustrated in FIGS. 17A-17D. In someembodiments, in response to receiving the deletion input, the userdevice removes (1816) from the handwriting input area (e.g., handwritinginput area 804 in FIG. 17E) the respective subset of the plurality ofhandwritten strokes corresponding to an end recognition unit (e.g., therecognition unit containing strokes 1726 and 1710) in a spatial sequenceformed by the plurality of recognition units in the handwriting inputarea. The end recognition unit corresponds to the end character (e.g.,the character “

”) in the multi-character recognition result (e.g., result 1728 in FIG.17E).

In some embodiments, the end recognition unit does not include (1818) atemporally final handwritten stroke among the plurality of handwrittenstrokes provided by the user. For example, if the user had provided thestroke 1718 after he or she has provided the strokes 1726 and 1710, theend recognition unit including the strokes 1726 and 1710 would still bedeleted first.

In some embodiments, in response to receiving an initial portion of thedeletion input, the user device visually distinguishes (1820) the endrecognition unit from other recognition units identified in thehandwriting input area, e.g., as illustrated in FIG. 17E. In someembodiments, the initial portion of the deletion input is (1822) aninitial contact detected on a delete button in the handwriting inputinterface, and the deletion input is detected when the initial contactis sustained for more than a predetermined threshold amount of time.

In some embodiments, the end recognition unit corresponds to ahandwritten Chinese character. In some embodiments, the handwritinginput is written in a cursive writing style. In some embodiments, thehandwriting input corresponds to multiple Chinese characters written ina cursive writing style. In some embodiments, at least one of thehandwritten strokes is divided into two adjacent recognition units ofthe plurality of recognition units. For example, sometimes, a user mayuse a long stroke that runs on into multiple characters, and in suchcases, the segmentation module of the handwriting input moduleoptionally divides the long stroke into several recognition units. Whenthe deletion of handwriting input is performed character-by-character(or recognition unit by recognition unit), only a segment of the longstroke is deleted at a time (e.g., the segment within a correspondingrecognition unit).

In some embodiments, the deletion input is (1824) a sustained contact ona deletion button provided in the handwriting input interface, andremoving the respective subset of the plurality of handwritten strokesfurther includes removing the subset of handwritten strokes in the endrecognition unit from the handwriting input area, stroke-by-stroke in areverse temporal order by which the subset of handwritten strokes hasbeen provided by the user.

In some embodiments, the user device generates (1826) a partialrecognition result comprising a subset of the respective charactersrecognized from the plurality of recognition units, where each of thesubset of the respective characters meets a predetermined confidencethreshold, e.g., as illustrated in FIGS. 17B and 17C. In someembodiments, the user device displays (1828) the partial recognitionresult (e.g., result 1712 in FIG. 17B and result 1720 in FIG. 17C)concurrently with the multi-character recognition result (e.g., results1714 and 1722) in the candidate display area of the handwriting inputinterface.

In some embodiments, the partial recognition result does not include atleast the end character in multi-character recognition result. In someembodiments, the partial recognition result does not include at least aninitial character in multi-character recognition result. In someembodiments, the partial recognition result does not include at least anintermediate character in multi-character recognition result.

In some embodiments, the smallest unit of deletion is a radical, andhandwriting inputs are deleted one radical at a time whenever a radicalhappens to be the last recognition unit in the handwriting inputs stillremaining in the handwriting input area.

As described herein, in some embodiments, the user device provides botha horizontal writing mode and a vertical writing mode. In someembodiments, the user device allows the user to enter text in one orboth of a left-to-right writing direction and a right-to-left directionin the horizontal writing mode. In some embodiments, the user deviceallows the user to enter text in one or both of a top-down writingdirection and a bottom-up direction in the vertical writing mode. Insome embodiments, the user device provides various affordances (e.g., awriting mode or writing direction button) on the user interface toinvoke a respective writing mode and/or writing direction for thecurrent handwriting inputs. In some embodiments, the text inputdirection in the text input area is the same as the handwriting inputdirection in the handwriting input direction by default. In someembodiments, the user device allows the user to manually set the inputdirection in the text input area and the writing direction in thehandwriting input area. In some embodiments, the text display directionin the candidate display area is the same as the handwriting inputdirection in the handwriting input area by default. In some embodiments,the user device allows the user to manually set the text displaydirection in the text input area independent of the handwriting inputdirection in the handwriting input area. In some embodiments, the userdevice associates the writing mode and/or writing direction of ahandwriting input interface with a corresponding device orientation, andchanges in the device orientation automatically triggers a change inwriting mode and/or writing direction. In some embodiments, a change inwriting direction automatically causes entry of a top-ranked recognitionresult to be entered into the text input area.

FIGS. 19A-19F illustrate exemplary user interfaces of a user device thatprovides both a horizontal input mode and a vertical input mode.

FIG. 19A shows the user device in a horizontal input mode. In someembodiments, the horizontal input mode is provided when the user deviceis in a landscape orientation, as shown in FIG. 19A. In someembodiments, the horizontal input mode is optionally associated with andprovided when the device is operated in the portrait orientation. Indifferent applications, the association between the device orientationand the writing mode may be different.

In the horizontal input mode, the user can provide handwrittencharacters in a horizontal writing direction (e.g., with a defaultwriting direction going from left to right, or a default writingdirection going from right to left). In the horizontal input mode, theuser device performs segmentation of the handwriting input into one ormore recognition units along the horizontal writing direction.

In some embodiments, the user device only permits single-line input inthe handwriting input area. In some embodiments, as shown in FIG. 19A,the user device allows multi-line input (e.g., two lines of input) inthe handwriting input area. In FIG. 19A, the user has provided aplurality of handwritten strokes in several rows in the handwritinginput area 806. Based on the sequence that the user has providedplurality of handwritten strokes and the relative locations of anddistances between the plurality of handwritten strokes, the user devicedetermines that the user has entered two lines of characters. Aftersegmenting the handwriting input into two separate lines, the devicedetermines the recognition unit(s) within each line.

As shown in FIG. 19A, the user device has recognized a respectivecharacter for each recognition unit identified in the currenthandwriting input 1902, and generated a number of recognition results1904 and 1906. As further shown in FIG. 19A, in some embodiments, if theoutput character (e.g. the letter “I”) for a particular set ofrecognition units (e.g., the recognition unit formed by the initialstroke) are low, the user device optionally generates a partialrecognition result (e.g., result 1906) that only shows the outputcharacters that have a sufficient recognition confidence. In someembodiments, the user may realize from the partial recognition result1906, that the first stroke can be revised or individually deleted orrewritten for the recognition model to produce the correct recognitionresult. In this particular example, editing of the first recognitionunit is not necessary because the first recognition unit 1904 does showthe desired recognition result for the first recognition unit.

In this example, as shown in FIG. 19A-19B, the user has rotated thedevice to a portrait orientation (e.g., shown in FIG. 19B). In responseto the change in device orientation, the handwriting input interface ischanged from the horizontal input mode to a vertical input mode, asshown in FIG. 19B. In the vertical input mode, the layout of thehandwriting input area 804, the candidate display area 806, and the textinput area 808 may be different from that shown in the horizontal inputmode. The particular layout of the horizontal and the vertical inputmodes can vary to suit different device shapes and application needs. Insome embodiments, with the rotation of the device orientation and thechange in input mode, the user device automatically enters thetop-ranked result (e.g., result 1904) as a text input 1910 into the textinput area 808. The orientation and position of the cursor 1912 alsoreflect the change in input mode and writing direction.

In some embodiments, the change in input mode is optionally triggered bythe user touching the special input mode selection affordance 1908. Insome embodiments, the input mode selection affordance is a graphicaluser interface element that also shows the current writing mode, thecurrent writing direction, and/or the current paragraph direction. Insome embodiments, the input mode selection affordance can cycle throughall available input modes and writing directions provided by thehandwriting input interface 802. As shown in FIG. 19A, the affordance1908 shows that the current input mode is a horizontal input mode, withthe writing direction from left to right, and a paragraph direction fromtop to bottom. In FIG. 19B, the affordance 1908 shows that the currentinput mode is a vertical input mode, with a writing direction from topto bottom, and a paragraph direction from right to left. Othercombinations of writing direction and paragraph direction are possible,in accordance with various embodiments.

As shown in FIG. 19C, the user has entered plurality of new strokes 1914(e.g., handwritten strokes for two Chinese characters “

”) in the handwriting input area 804 in the vertical input mode. Thehandwriting input is written in the vertical writing direction. The userdevice segments the handwriting input in the vertical direction into tworecognition units, and displays two recognition results 1916 and 1918each including two recognized characters laid out in the verticaldirection.

FIGS. 19C-19D illustrate that, when the user selects a displayedrecognition result (e.g., result 1916), the selected recognition resultis entered into the text input area 808 in the vertical direction.

FIGS. 19E-19F illustrate that, the user has entered additional lines ofhandwriting input 1920 in the vertical writing direction. The lines runfrom left to right in accordance with the paragraph direction oftraditional Chinese writing. In some embodiments, the candidate displayarea 806 also shows the recognition results (e.g., results 1922 and1924) in the same writing direction and paragraph direction as that forthe handwriting input area. In some embodiments, other writing directionand paragraph direction can be provided by default in accordance with aprimary language associated with the user device, or the language (e.g.,Arabic, Chinese, Japanese, English, etc.) of a soft keyboard installedon the user device.

FIGS. 19E-19F also show that, when the user has selected a recognitionresult (e.g., result 1922), the text of the selected recognition resultis entered into the text input area 808. As shown in FIG. 19F, the textinput currently in the text input area 808 thus includes both textwritten in a horizontal mode, with a writing direction from left toright, and text written in the vertical mode, with a top-down writingdirection. The paragraph direction for the horizontal text is top-down,while the paragraph direction for the vertical text is from right toleft.

In some embodiments, the user device allows the user to separatelyestablish preferred writing directions, paragraph directions for each ofthe handwriting input area 804, the candidate display area 806, and thetext input area 808. In some embodiments, the user device allows theuser to establish the preferred writing direction and paragraphdirection for each of the handwriting input area 804, the candidatedisplay area 806, and the text input area 808, to be associated witheach device orientation.

FIGS. 20A-20C are flow charts of an exemplary process 2000 for changingthe text input direction and the handwriting input direction of the userinterface. FIGS. 19A-19F illustrate the process 2000 in accordance withsome embodiments.

In some embodiments, the user device determines (2002) an orientation ofthe device. The orientation of the device and the changes in deviceorientation can be detected by the accelerometer and/or otherorientation sensing element in the user device. In some embodiments, theuser device provides (2004) a handwriting input interface on the devicein a horizontal input mode in accordance with the device being in afirst orientation. A respective line of handwriting input entered in thehorizontal input mode is segmented into one or more respectiverecognition units along a horizontal writing direction. In someembodiments, the device provides (2006) the handwriting input interfaceon the device in a vertical input mode in accordance with the device ina second orientation. A respective line of handwriting input entered inthe vertical input mode is segmented into one or more respectiverecognition units along a vertical writing direction.

In some embodiments, while operating in the horizontal input mode(2008): the device detects (2010) a change in device orientation fromthe first orientation to the second orientation. In some embodiments, inresponse to the change in device orientation, the device switches (2012)from the horizontal input mode to the vertical input mode. This isillustrated, for example, in FIGS. 19A-19B. In some embodiments, whileoperating in the vertical input mode (2014): the user device detects(2016) a change in device orientation from the second orientation to thefirst orientation. In some embodiments, in response to the change indevice orientation, the user device switches (2018) from the verticalinput mode to the horizontal input mode. In some embodiments, theassociation between device orientation and the input mode may beopposite of that described above.

In some embodiments, while operating in the horizontal input mode(2020): the user device receives (2022) a first multi-word handwritinginput from the user. In response to the first multi-word handwritinginput, the user device presents (2024) a first multi-word recognitionresult in a candidate display area of the handwriting input interface inaccordance with the horizontal writing direction. This is illustrated,for example, in FIG. 19A. In some embodiments, while operating in thevertical input mode (2026): the user device receives (2028) a secondmulti-word handwriting input from the user. In response to the secondmulti-word handwriting input, the user device presents (2030) a secondmulti-word recognition result in the candidate display area inaccordance with the vertical writing direction. This is illustrated, forexample, in FIGS. 19C and 19E.

In some embodiments, the user device receives (2032) a first user inputselecting the first multi-word recognition result, e.g., as shown inFIGS. 19A-19B where the selection is made implicitly with an input(e.g., rotation of device or selection of affordance 1908) for changingthe input direction. The user device receives (2034) a second user inputselecting the second multi-word recognition result, e.g., as shown inFIG. 19C or FIG. 19E. The user device concurrently displays (2036)respective text of the first multi-word recognition result and thesecond multi-word recognition result in a text input area of thehandwriting input interface, where the respective text of the firstmulti-word recognition result is displayed in accordance with thehorizontal writing direction, and the respective text of the secondmulti-word recognition result is displayed in accordance with thevertical writing direction. This is illustrated in text input area 808in FIG. 19F, for example.

In some embodiments, the handwriting input area accepts multiple linesof handwriting input in the horizontal writing direction and has adefault top-down paragraph direction. In some embodiments, thehorizontal writing direction is from left to right. In some embodiments,the horizontal writing direction is from right to left. In someembodiments, the handwriting input area accepts multiple lines ofhandwriting input in the vertical writing direction and has a defaultleft-to-right paragraph direction. In some embodiments, the handwritinginput area accepts multiple lines of handwriting input in the verticalwriting direction and has a default right-to-left paragraph direction.In some embodiments, the vertical writing direction is from top tobottom. In some embodiments, the first orientation is a landscapeorientation by default, and the second orientation is a portraitorientation by default. In some embodiments, the user device provides arespective affordance in the handwriting input interface for manuallyswitching between the horizontal input mode and the vertical input mode,irrespective of the device orientation. In some embodiments, the userdevice provides a respective affordance in the handwriting inputinterface for manually switching between two alternative writingdirections. In some embodiments, the user device provides a respectiveaffordance in the handwriting input interface for manually switchingbetween two alternative paragraph directions. In some embodiments, theaffordance is a toggle button that rotates through each availablecombination of the input and paragraph directions, when invoked one ormore consecutive times.

In some embodiments, the user device receives (2038) a handwriting inputfrom a user. The handwriting input includes a plurality of handwrittenstrokes provided in the handwriting input area of the handwriting inputinterface. In response to the handwriting input, the user devicedisplays (2040) one or more recognition results in a candidate displayarea of the handwriting input interface. While the one or morerecognition results are displayed in the candidate display area, theuser device detects (2042) a user input for switching from a currenthandwriting input mode to an alternative handwriting input mode. Inresponse to the user input (2044): the user device switches (2046) fromthe current handwriting input mode to the alternative handwriting inputmode. In some embodiments, the user device clears (2048) the handwritinginput from the handwriting input area. In some embodiments, the userdevice automatically enters (2050) a top-ranked recognition result ofthe one or more recognition results displayed in the candidate displayarea into a text input area of the handwriting input interface. This isillustrated in FIGS. 19A-19B, for example, where the current handwritinginput mode is the horizontal input mode, and the alternative handwritinginput mode is the vertical input mode. In some embodiments, the currenthandwriting input mode is the vertical input mode, and the alternativehandwriting input mode is the horizontal input mode. In someembodiments, the current handwriting input mode and the alternativehandwriting input mode are modes under which any two differenthandwriting input directions or paragraph directions are provided. Insome embodiments, the user input is (2052) rotation of the device from acurrent orientation to a different orientation. In some embodiments, theuser input is invocation of an affordance to manually switch the currenthandwriting input mode to the alternative handwriting input mode.

As described herein, the handwriting input module allows the user toenter handwritten strokes and/or characters in any temporal order. Thus,deleting an individual handwritten character in a multi-characterhandwriting input, and rewriting the same or a different handwrittencharacter in the same location as the deleted character is advantageous,because it would help the user revise a long handwriting input withouthaving to delete the whole handwriting input.

FIGS. 20A-20H illustrate exemplary user interfaces for visuallyhighlighting and/or deleting a recognition unit identified in aplurality of handwritten strokes currently accumulated in thehandwriting input area. Allowing the user to individually select, view,and delete any one of multiple recognition units identified in aplurality inputs is particularly useful when multi-character, and evenmulti-line handwriting input is permitted by the user device. Byallowing the user to delete a particular recognition unit in thebeginning or the middle of the handwriting inputs allows to the user tomake corrections to a long input, without requiring the user to deleteall recognition units positioned after an undesirable recognition unit.

As shown in FIGS. 21A-21C, the user has provided a plurality ofhandwritten strokes (e.g., strokes 2102, 2104, and 2106) in thehandwriting input area 804 of the handwriting input user interface 802.While the user continues to provide additional strokes to thehandwriting input area 804, the user device updates the recognitionunits identified from the handwriting input currently accumulated in thehandwriting input area, and revises the recognition results according tothe output characters recognized from the updated recognition units. Asshown in FIG. 20C, the user device has identified two recognition unitsfrom the current handwriting input, and presented three recognitionresults (e.g., 2108, 2010, and 2112) each including two Chinesecharacters.

In this example, after the user has written the two handwritingcharacters, the user realizes that the first recognition unit isincorrectly written, and as a result, the user device has not identifiedand presented the desired recognition result in the candidate displayarea.

In some embodiments, when the user provides a tap gesture (e.g., acontact followed with an immediate lift-off at the same location) on thetouch-sensitive display, the user device interprets the tap gesture asan input to cause visually highlighting of individual recognition unitsthat are currently identified in the handwriting input area. In someembodiments, another predetermined gesture (e.g., a multi-finger wipinggesture over the handwriting input area) is used to cause the userdevice to highlight the individual recognition units in the handwritinginput area 804. A tap gesture is sometimes preferred because it isrelatively easy to distinguish from a handwritten stroke, which usuallyinvolves a sustained contact of a longer duration and with movement ofthe contact within the handwriting input area 804. A multi-touch gestureis sometimes preferred because it is relatively easy to distinguish froma handwritten stroke, which usually involves a single contact within thehandwriting input area 804. In some embodiments, the user deviceprovides an affordance 2112 in the user interface that can be invoked(e.g., via a contact 2114) by the user to cause the individualrecognition units to be visually highlighted (e.g., as shown by boxes2108 and 2110). In some embodiments, the affordance is preferred whenthere is sufficient screen space to accommodate such an affordance. Insome embodiments, the affordance can be invoked multiple consecutivetimes by the user, which causes the user device to visually highlightrecognition unit(s) identified according to a different segmentationchain in the segmentation lattice and for the highlighting to be turnedoff when all segmentation chains have been shown.

As shown in FIG. 21D, when the user has provided the necessary gestureto highlight the individual recognition units in the handwriting inputarea 804, the user device further displays a respective deletingaffordance (e.g., small delete buttons 2116 and 2118) over eachhighlighted recognition unit. FIGS. 21E-21F show that when the usertouches (e.g., via a contact 2120) the deleting affordance of arespective recognition unit (e.g., the delete button 2116 for the firstrecognition unit in box 2118), the respective recognition unit (e.g., inbox 2118) is removed from the handwriting input area 804. In thisparticular example, the deleted recognition unit is not the last enteredrecognition unit temporally, nor is it the spatially last recognitionunit along the writing direction. In other words, the user can deleteany recognition unit regardless of when and where it has been providedin the handwriting input area. FIG. 21F shows that, in response to thedeletion of the first recognition unit in the handwriting input area,the user device also updates the recognition results displayed in thecandidate display area 806. As shown in FIG. 21F, the user device hasalso deleted candidate character corresponding to the deletedrecognition unit from the recognition results. As a result, a newrecognition result 2120 is shown in the candidate display area 806.

As shown in FIGS. 21G-21H, after the first recognition unit has beenremoved from the handwriting input interface 804, the user has provideda plurality of new handwritten strokes 2122 in the area that waspreviously occupied by the deleted recognition unit. The user device hasre-segmented the currently accumulated handwriting input in thehandwriting input area 804. Based on the recognition units identifiedfrom the handwriting input, the user device regenerated recognitionresults (e.g., results 2124 and 2126) in the candidate display area 806.FIG. 21G-21H show that the user has selected (e.g., via the contact2128) one of the recognition results (e.g., result 2124), and text ofthe selected recognition result is entered into the text input area 808.

FIGS. 22A-22B are flow charts for an exemplary process 2200 in whichindividual recognition units identified in the current handwriting inputis visually presented, and can be individually deleted, regardless ofthe temporal order by which the recognition units are formed. FIGS.21A-21H illustrate the process 2200 in accordance with some embodiments.

In the exemplary process 2200, the user device receives (2202) ahandwriting input from a user. The handwriting input includes aplurality of handwritten strokes provided on a touch-sensitive surfacecoupled to the device. In some embodiments, the user device renders(2204) the plurality of handwritten strokes in a handwriting input area(e.g., handwriting input area 804) of a handwriting input interface. Insome embodiments, the user device segments (2206) the plurality ofhandwritten strokes into two or more recognition units, each recognitionunit comprising a respective subset of the plurality of handwrittenstrokes.

In some embodiments, the user device receives (2208) an edit requestfrom the user. In some embodiments, the edit request is (2210) a contactdetected over a predetermined affordance (e.g., affordance 2112 in FIG.21D) provided in the handwriting input interface. In some embodiments,the edit request is (2212) a tap gesture detected over a predeterminedarea in the handwriting input interface. In some embodiments, thepredetermined area is within the handwriting input area of thehandwriting input interface. In some embodiments, the predetermined areais outside of the handwriting input area of the handwriting inputinterface. In some embodiments, another predetermined gesture (e.g., across gesture, a horizontal swipe gesture, a vertical swipe gesture, aslanted swipe gesture) outside of the handwriting input area can be usedas an edit request. Gestures outside of the handwriting input area canbe easily distinguished from a handwritten stroke, since it is providedoutside of the handwriting input area.

In some embodiments, in response to the edit request, the user devicevisually distinguishes (2214) the two or more recognition units in thehandwriting input area, e.g., using the boxes 2108 and 2110 in FIG. 21D.In some embodiments, visually distinguishing the two or more recognitionunits further includes (2216) highlighting respective boundaries betweenthe two or more recognition units in the handwriting input area. Invarious embodiments, different ways of visually distinguishing therecognition units identified in the current handwriting input may beused.

In some embodiments, the user device provides (2218) a means forindividually deleting each of the two or more recognition units from thehandwriting input area. In some embodiments, the means for individuallydeleting each of the two or more recognition units is a respectivedelete button displayed in proximity to the each recognition unit, e.g.,as shown by delete buttons 2116 and 2118 in FIG. 21D. In someembodiments, the means for individually deleting each of the two or morerecognition units is a means for detecting a predetermined deletiongesture input over the each recognition unit. In some embodiments, theuser device does not visibly display the individual deletion affordanceover the highlighted recognition units. Instead, in some embodiments,the user is allowed to use a deletion gesture to delete a respectiverecognition unit underneath the deletion gesture. In some embodiments,as the user device is displaying the recognition units in a visuallyhighlighted manner, the user device does not accept additionalhandwritten strokes in the handwriting input area. Instead, apredetermined gesture or any gesture detected over a visuallyhighlighted recognition unit will cause the user device to remove therecognition unit from the handwriting input area, and revise therecognition results displayed in the candidate display area accordingly.In some embodiments, a tap gesture causes the user device to visuallyhighlight the individual recognition units identified in the handwritingrecognition area, and the user can then use the delete button to deletethe individual recognition units one by one in the reverse writingdirection.

In some embodiments, the user device receives (2224), from the user andthrough the provided means, a deletion input for individually deleting afirst recognition unit of the two or more recognition units from thehandwriting input area, e.g., as shown in FIG. 21E. In response to thedeletion input, the user device removes (2226) the respective subset ofhandwritten strokes in the first recognition unit from the handwritinginput area, e.g., as shown in FIG. 21F. In some embodiments, the firstrecognition unit is a spatially initial recognition unit in the two ormore recognition units. In some embodiments, the first recognition unitis a spatially intermediate recognition unit among the two or morerecognition units, e.g., as shown in FIGS. 21E-21F. In some embodiments,the first recognition unit is a spatially end recognition unit among thetwo or more recognition units.

In some embodiments, the user device generates (2228) a segmentationlattice from the plurality of handwritten strokes, the segmentationlattice includes a plurality of alternative segmentation chains eachrepresenting a respective set of recognition units identified from theplurality of handwriting strokes. For example, FIG. 21G shows therecognition results 2024 and 2026, where the recognition result 2024 isgenerated from one segmentation chain with two recognition units, andthe recognition result 2026 is generated from another segmentation chainwith three recognition units. In some embodiments, the user devicereceives (2230) two or more consecutive edit requests from the user. Forexample, the two or more consecutive edit request can be severalconsecutive taps on the affordance 2112 in FIG. 21G. In someembodiments, in response to each of the two or more consecutive editrequests, the user device visually distinguishes (2232) the respectiveset of recognition units from a different one of the plurality ofalternative segmentation chains in the handwriting input area. Forexample, in response to a first tap gesture, two recognition units(e.g., for the characters “

” and “

”, respectively) are highlighted in the handwriting input area 804, andin response to a second tap gesture, three recognition units (e.g., forthe characters “

”, “

”, and “

”, respectively). In some embodiments, in response to a third tapgesture, the visual highlighting is optionally removed from allrecognition units, and the handwriting input area is returned to thenormal state ready to accept additional strokes. In some embodiments,the user device provides (2234) a means for individually deleting eachof the respective set of recognition units currently represented in thehandwriting input area. In some embodiments, the means is an individualdelete button for each highlighted recognition unit. In someembodiments, the means is a means for detecting of a predetermineddeletion gesture over each highlighted recognition unit, and forinvoking a function to delete the highlighted recognition unit under thepredetermined deletion gesture.

As described herein, in some embodiments, the user device provides acontinuous input mode in the handwriting input area. Since the area ofthe handwriting input area is limited on a portable user device, it issometimes desirable to provide a way to cache the handwriting inputsprovided by the user, and allow the user to reuse the screen spacewithout commit the previously provided handwriting inputs. In someembodiments, the user device provides a scrolling handwriting inputarea, where input area gradually shifts by a certain amount (e.g., onerecognition unit at a time) when the user is getting sufficiently closeto the end of the handwriting input area. In some embodiments, sinceshifting the existing recognition units in the handwriting input areamay interfere with the user's writing process, and possibly interferewith the correct segmentation of the recognition units, it is sometimesadvantageous to recycle a previously used region of the input areawithout dynamically shifting the recognition units. In some embodiments,when the user reuses an area that is occupied by a handwriting inputthat has not yet been entered into the text input area, a toprecognition result for the handwriting input area is automaticallyentered into the text input area, such that the user can continueproviding a new handwriting input without explicitly selecting thetop-ranked recognition result.

In some conventional systems, the user is allowed to write over anexisting handwriting input that is still shown in the handwriting inputarea. In such systems, temporal information is used to determine whethera new stroke is part of an earlier recognition unit or a new recognitionunit. Such temporal-information dependent systems place stringentrequirements on the speed and tempo by which the user provides thehandwriting input, which is difficult to meet by many users. Inaddition, the visual rendering of the handwriting input can be a jumblethat is difficult to for the user to decipher. Thus, the writing processcan be frustrating, and confusing for the user, leading to a bad userexperience.

As described herein, a fading process is used to indicate when the usercan reuse an area occupied by a previously written recognition unit, andcontinue writing in the handwriting input area. In some embodiments, thefading process gradually reduces the visibility of each recognition unitthat has been provided in the handwriting input area for a thresholdamount of time, such that when new strokes are written over it, theexisting text does not visually compete with the new strokes. In someembodiments, writing over a faded recognition unit automatically causesa top-ranked recognition result for the recognition unit to be enteredinto the text input area, without requiring the user to stop writing andto explicitly provide a selection input for the top-ranked recognitionresult. This implicit and automatic confirmation of the top-rankedrecognition result improves the input efficient and speed of thehandwriting input interface, and reduces the cognitive burden placed onthe user to maintain the thought flow of the current text composition.In some embodiments, writing over a faded recognition unit does notcause automatic selection of the top-ranked search result. Instead, thefaded recognition units are cached in a handwriting input stack, andcombined with the new handwriting input as the current handwritinginput. The user can see a recognition results generated based on all ofthe recognition units accumulated in the handwriting input stack beforemaking a selection.

FIGS. 23A-23J illustrate exemplary user interfaces and processes inwhich recognition units provided in different region of the handwritinginput area are gradually faded out from their respective regions, e.g.,after a predetermined amount of time and after the fade-out has occurredin a particular region, the user is allowed to provide new handwrittenstrokes in that region.

As shown in FIG. 23A, the user has provided a plurality of handwrittenstrokes 2302 (e.g., three handwritten strokes for the capital letter“I”) in the handwriting input area 804. The handwritten strokes 2302 areidentified by the user device as a recognition unit. In someembodiments, the handwriting input currently shown in the handwritinginput area 804 is cached in a first layer in the handwriting input stackof the user device. A number of recognition results generated based onthe identified recognition unit are provided in the candidate displayarea 804.

FIG. 23B shows that, when the user continues to write one or morestrokes 2302 to the right of the strokes 2304, the handwritten strokes2302 in the first recognition unit starts to fade out gradually in thehandwriting input area 804. In some embodiments, an animation isdisplayed to mimic the gradual fading or dissipation of the visualrendering of the first recognition unit. For example, the animation mayproduce a visual effect of ink evaporating from a white board. In someembodiments, the fading of the recognition unit is not uniform acrossthe entire recognition unit. In some embodiments, the fading of therecognition unit increases over time and eventually the recognition unitis completely invisible in the handwriting area. However, even thoughthe recognition unit is no longer visible in the handwriting input area804, in some embodiments, the invisible recognition unit remains at thetop of the handwriting input stack, and the recognition resultsgenerated from the recognition unit continue to be displayed in thecandidate display area. In some embodiments, a faded recognition unit isnot completely removed from view until new handwriting input has beenwritten over it.

In some embodiments, the user device allows new handwriting input to beprovided over the region occupied by a faded recognition unit immediateupon the start of the fading animation. In some embodiments, the userdevice allows new handwriting input to be provided over the regionoccupied by a faded recognition unit only after the fading hasprogressed to a certain stage (e.g., to the faintest level or until therecognition is completely invisible in the region).

FIG. 23C shows that the first recognition unit (i.e., strokes 2302) hascompleted its fading process (e.g., the ink color has stabilized at veryfaint level or has become invisible). The user device has identifiedadditional recognition units from the additional handwritten strokesprovided by the user (e.g., the recognition units for the handwrittenletters “a” and “m”), and updated the recognition results presented inthe candidate display area 804.

FIGS. 22D-22F illustrate that, as time goes on, and the user hasprovided a plurality of addition handwritten strokes (e.g., 2304 and2306) in the handwriting input area 804. At the same time, thepreviously identified recognition units gradually fade away from thehandwriting input area 804. In some embodiments, it takes apredetermined amount of time for each recognition unit to start its ownfading process after the recognition unit has been identified. In someembodiments, the fading process for each recognition unit does not startuntil the user has started inputting a second recognition unitdownstream from it. As shown in FIGS. 23B-23F, when the handwritinginput is provided in a cursive style, a single stroke (e.g., stroke 2304or stroke 2306) may run through multiple recognition units (e.g.,recognition unit for each handwritten letter in the word “am” or “back”)in the handwriting input area.

FIG. 22G illustrate that, even after a recognition unit has started itsfading process, the user can bring it back to the un-faded state by apredetermined revival input, e.g., a tap gesture (e.g., as indicated bya contact 2308 followed by an immediate lift-off) on a delete button2310. When the recognition units are revived, its appearance returns tothe normal visibility level. In some embodiments, the revival of fadedrecognition units is made character-by-character in the reverse writingdirection in the handwriting input area 804. In some embodiments, therevival of faded recognition units is made word-by-word in thehandwriting input area 804. As shown in FIG. 23G, the recognition unitscorresponding to the word “back” has been revived from a completed fadedstate to a completely un-faded state. In some embodiments, the clock forstarting the fading process is reset each recognition unit when therecognition unit is revived into the un-faded state.

FIG. 22H shows that, a sustained contact on the delete button causes thelast recognition unit (e.g., the recognition unit for the letter “k” inthe word “back”) in the default writing direction to be deleted from thehandwriting input area 804. As the deletion input is continuallymaintained, more recognition units (e.g., the recognition units for theletters “c”, “a”, “b” in the word “back”) are deleted one by one in thereverse writing direction. In some embodiments, the deletion of therecognition unit is word by word, and all letters of the handwrittenword “back” is deleted from the handwriting input area 804 are removedat the same time. FIG. 22H also shows that, as the contact 2308 ismaintained on the delete button 2310 after the deletion of therecognition unit for the letter “b” in the handwritten word “back”, thepreviously faded recognition unit “m” is revived as well.

FIG. 23I shows that, if the delete input ceases before the deletion ofthe revived recognition unit “m” in the handwritten word “am” occurs,the revived recognition unit gradually fades again. In some embodiments,the state (e.g., a state selected from a set of one or more faded statesand the un-faded state) of each recognition unit is maintained andupdated in the handwriting input stack.

FIG. 23J illustrate that, when the user has provided one or more strokes2312 over the area occupied by a faded recognition unit (e.g., therecognition unit for the letter “I”) in the handwriting input area, insome embodiments, text of the top-ranked recognition result (e.g.,result 2314) for the handwriting input made before the strokes 2312 areautomatically entered into the text input area 808, as shown in FIGS.23I-23J. As shown in FIG. 23J, the text “I am” is no longer shown asbeing tentative, but instead, has been committed in the text input area808. In some embodiments, once a text input has been made for a fully orpartially faded handwriting input, the handwriting input is removed fromthe handwriting input stack. The newly entered strokes (e.g., strokes2312) become the current input in the handwriting input stack.

As shown in FIG. 23J, the text “I am” is no longer shown as beingtentative, but instead, has been committed in the text input area 808.In some embodiments, once a text input has been made for a fully orpartially faded handwriting input, the handwriting input is removed fromthe handwriting input stack. The newly entered strokes (e.g., strokes2312) become the current input in the handwriting input stack.

In some embodiments, when the strokes 2312 is provided over the areaoccupied by a faded recognition unit (e.g., the recognition unit for theletter “I”) in the handwriting input area, the text of the top-rankedrecognition result (e.g., result 2314) for the handwriting input madebefore the strokes 2312 are not automatically entered into the textinput area 808. Instead, the currently handwriting input (both faded andun-faded) in the handwriting input area 804 is cleared, and cached inthe handwriting input stack. The new strokes 2312 appended to the cachedhandwriting input in the handwriting input stack. The user devicedetermines the recognition results based on the entirety of thehandwriting input currently accumulated in the handwriting input stack.The recognition results are displayed in the candidate display area. Inother words, even though only a part of the currently accumulatedhandwriting input is shown in the handwriting input area 804, therecognition results are generated based on the entire handwriting inputcached in the handwriting input stack (both the portion that is visibleand the portions that are no longer visible).

FIG. 23K shows that the user has entered more strokes 2316 in thehandwriting input area 804, which has become faded over time. FIG. 23Lshows that a new stroke 2318 written over the faded strokes 2312 and2316, has caused text of the top recognition result 2320 for the fadedstrokes 2312 and 2316 to be entered into the text input area 808.

In some embodiments, the user optionally provides a handwriting input inmultiple lines. In some embodiments, the same fading process can be usedto clear the handwriting input area for a new handwriting input, whenmulti-line input is enabled.

FIGS. 24A-24B are flow charts of an exemplary process 2400 for providinga fading process in the handwriting input area of a handwriting inputinterface. FIGS. 23A-23K illustrate the process 2400 in accordance withsome embodiments.

In some embodiments, the device receives (2402) a first handwritinginput from a user. The first handwriting input includes a plurality ofhandwritten strokes, and the plurality of handwritten strokes formmultiple recognition units distributed along a respective writingdirection associated with a handwriting input area of a handwritinginput interface. In some embodiments, the user device renders (2404)each of the plurality of handwritten strokes in the handwriting inputarea as the handwritten stroke is provided by the user.

In some embodiments, the user device starts (2406) a respective fadingprocess for each of the multiple recognition units after the recognitionunit is completely rendered. In some embodiments, during the respectivefading process, the rendering of the recognition unit in the firsthandwriting input fades away. This is illustrated in FIGS. 23A-23F inaccordance with some embodiments.

In some embodiments, the user device receives (2408) a secondhandwriting input from the user over a region of the handwriting inputarea occupied by a faded recognition unit of the multiple recognitionunit, e.g., as illustrated in FIGS. 231-23J, and 23K-23L. In someembodiments, in response to receiving the second handwriting input(2410): the user device renders (2412) the second handwriting input inthe handwriting input area and clears (2414) all faded recognition unitsfrom the handwriting input area. In some embodiments, all recognitionunits that were entered in the handwriting input area before the secondhandwriting input are cleared from the handwriting input area,regardless of whether the recognition unit has started its fadingprocess. This is illustrated in FIGS. 23I-23J, and 23K-23L, for example.

In some embodiments, the user device generates (2416) one or morerecognition results for the first handwriting input. In someembodiments, the user device displays (2418) the one or more recognitionresults in a candidate display area of the handwriting input interface.In some embodiments, in response to receiving the second handwritinginput, the user device, automatically, without user selection, enters(2420) a top-ranked recognition result displayed in the candidatedisplay area into a text input area of the handwriting input interface.This is illustrated in FIG. 23I-23J and 23K-23L, for example.

In some embodiments, the user device stores (2422) an input stackincluding the first handwriting input and the second handwriting input.In some embodiments, the user device generates (2424) one or moremulti-character recognition results each comprising a respective spatialsequence of characters recognized from a concatenation of the firsthandwriting input and the second handwriting input. In some embodiments,the user device displays (2426) the one or more multi-characterrecognition results in a candidate display area of the handwriting inputinterface, while the rendering of the second handwriting input hasreplaced the rendering of the first handwriting input in the handwritinginput area.

In some embodiments, the respective fading process for each recognitionunit is started when a predetermined time period has elapsed after therecognition unit is completed by the user.

In some embodiments, fading process for each recognition unit is startedwhen the user has started inputting the strokes for a next recognitionunit after the recognition unit.

In some embodiments, an end state of the respective fading process foreach recognition unit is a state with a predetermined minimum visibilityfor the recognition unit.

In some embodiments, an end state of the respective fading process foreach recognition unit is a state with zero visibility for therecognition unit.

In some embodiments, after a last recognition unit in the firsthandwriting input has become faded, the user device receives (2428) apredetermined revival input from the user. In response to receiving thepredetermined revival input, the user device reverts (2430) the lastrecognition unit from the faded state to an un-faded state. This isillustrated in FIGS. 23F-23H, for example. In some embodiments, thepredetermined revival input is an initial contact detected on a deletionbutton provided in the handwriting input interface. In some embodiments,a sustained contact detected on the deletion button deletes the lastrecognition unit from the handwriting input area and revives the secondto last recognition unit from the faded state to the un-faded state.This is illustrated in FIGS. 23G-23H, for example.

As described herein, the multi-script handwriting recognition modelperforms stroke-order independent, and stroke-direction independentrecognition of handwritten characters. In some embodiments, therecognition model is trained on only spatially-derived featurescontained in flat images of writing samples corresponding to differentcharacters in the vocabulary of the handwriting recognition model. Sincethe images of the writing sample do not contain any temporal informationrelated to individual strokes contained in the images, the resultingrecognition model is stroke-order independent and stroke-directionindependent.

As illustrated above, stroke-order and stroke-direction independenthandwriting recognition provide many advantages over conventionalrecognition systems that rely on information related to the temporalgeneration of the characters (e.g., temporal sequences of strokes in thecharacters). However, in real-time handwriting recognition scenarios,temporal information related to individual strokes is available, and itis sometimes beneficial to utilize this information to improverecognition accuracy of the handwriting recognition system. The followdescribe a technique that integrates temporally-derivedstroke-distribution information into the spatial feature extraction of ahandwriting recognition model, where the use of the temporally-derivedstroke-distribution information does not destroy the stroke-order and/orstroke direction independence of the handwriting recognition system.Based on the stroke-distribution information related to differentcharacters, disambiguation between similar-looking characters that areproduced with distinctively different set of strokes becomes possible.

In some embodiments, when a handwriting input is converted to an inputimage (e.g., an input bitmap image) for the handwriting recognitionmodel (e.g., a CNN), the temporal information associated with individualstrokes is lost. For example, for a Chinese character “

”, eight strokes (e.g., labeled #1-#8 in FIG. 27) can be used to writeout the Character. The sequence and direction of the strokes for thecharacter provides some unique features associated with the character. Anaïve way to capture the stroke-order and stroke-direction information,without destroying the stroke-order and stroke-direction independence ofthe recognition system is to explicitly enumerate all possiblepermutations in stroke order and stroke direction in the trainingsamples. But even for a character of only moderate complexity, thiswould amount to over one billion possibilities, which makes itunfeasible if not impossible to implement in practice. As describedherein, a stroke-distribution profile is generated for each writingsample, which abstract out the chronological aspects of strokegeneration (i.e., temporal information). The stroke-distributionprofiles of writing samples are trained to extract a set oftemporally-derived features which are subsequently combined with thespatially-derived features (e.g., from input bitmap images), to improverecognition accuracy without impacting the stroke-order and strokedirection independence of the handwriting recognition system.

As described herein, the temporal information associated with acharacter is extracted by computing a variety of pixel distributions tocharacterize each handwritten stroke. Every handwritten stroke of acharacter gives rise to a deterministic pattern (or profile) whenprojected onto a given direction. While this pattern in and of itselfmay be insufficient to recognize the stroke unambiguously, when combinedwith other similar patterns, it may be adequate to capture certaincharacteristics inherent to this particular stroke. Integrating thiskind of stroke representation alongside spatial feature extraction(e.g., feature extraction based on input images in a CNN) in turnprovides orthogonal information that can be useful to disambiguatebetween similar-looking characters in the repertoire of the handwritingrecognition model.

FIGS. 25A-25B are flow charts of an exemplary process 2500 forintegrating temporally-derived features and spatially-derived featuresof handwriting samples during training of a handwriting recognitionmodel, where the resulting recognition model remains stroke-order andstroke direction independent. In some embodiments, the exemplary process2500 is performed on a server device that provides the trainedrecognition model to a user device (e.g., a portable device 100). Insome embodiments, the server device includes one or more processors andmemory containing instructions for performing the process 2500 whenexecuted by the one or more processors.

In the exemplary process 2500, the device separately trains (2502) a setof spatially-derived features and a set of temporally-derived featuresof a handwriting recognition model, where the set of spatially-derivedfeatures are trained on a corpus of training images each being an imageof a handwriting sample for a respective character of an outputcharacter set, and the set of temporally-derived features are trained ona corpus of stroke-distribution profiles, each stroke-distributionprofile numerically characterizing a spatial distribution of a pluralityof strokes in a handwriting sample for a respective character of theoutput character set.

In some embodiments, separately training the set of spatially-derivedfeatures further includes (2504) training a convolutional neural networkhaving an input layer, an output layer, and a plurality of convolutionallayers including a first convolutional layer, a last convolutionallayer, zero or more intermediate convolutional layers between the firstconvolutional layer and the last convolutional layer, and a hidden layerbetween the last convolutional layer and the output layer. An exemplaryconvolutional network 2602 is shown in FIG. 26. The exemplaryconvolutional network 2602 can be implemented in substantially the sameway as the convolutional network 602 shown in FIG. 6. The convolutionalnetwork 2602 includes an input layer 2606, an output layer 2608, aplurality of convolutional layers including a first convolutional layer2610 a, zero or more intermediate convolutional layers, and a lastconvolutional layer 2610 n, and a hidden layer 2614 between the lastconvolutional layer and the output layer 2608. The convolutional network2602 also includes kernel layers 2616 and sub-sampling layers 2612 inaccordance with the arrangement shown in FIG. 6. The training of theconvolutional network is based on images 2614 of writing samples in thetraining corpus 2604. Spatially-derived features are obtained andrespective weights associated with the different features are determinedby minimizing the recognition errors for the training samples in thetraining corpus. The same features and weights, once trained, are usedfor recognition of new handwriting samples not present in the trainingcorpus.

In some embodiments, separately training the set of temporally-derivedfeatures further includes (2506) providing the plurality ofstroke-distribution profiles to a statistical model to determine aplurality of temporally-derived parameters and respective weights forthe plurality of temporally-derived parameters for classifying therespective characters of the output character set. In some embodiments,as shown in FIG. 26, a stroke-distribution profile 2620 is derived fromeach writing sample in a training corpus 2622. The training corpus 2622optionally includes the same writing samples as the corpus 2604, butalso includes temporal information associated with stroke generation ineach writing sample. The stroke-distribution profiles 2622 are providedto a statistical modeling process 2624, during which temporally-derivedfeatures are extracted and respective weights for the different featuresare determined by minimizing a recognition or classification error basedon a statistical modeling method (e.g., a CNN, K-Nearest Neighbor,etc.). As shown in FIG. 26, the set of temporally derived features andrespective weights are converted to a set of feature vectors (e.g.,feature vectors 2626 or feature vectors 2628) and injected into arespective layer in the convolutional neural network 2602. The resultingnetwork thus includes spatially-derived parameters andtemporally-derived parameters that are orthogonal to each other, andtogether contribute to the recognition of characters.

In some embodiments, the device combines (2508) the set ofspatially-derived features and the set of temporally-derived features inthe handwriting recognition model. In some embodiments, combining theset of spatially-derived features and the set of temporally-derivedfeatures in the handwriting recognition model includes (2510) injectingthe plurality of spatially-derived parameters and the plurality oftemporally-derived parameters into one of the convolutional layers orthe hidden layer of the convolutional neural network. In someembodiments, the plurality of temporally-derived parameters andrespective weights for the plurality temporally-derived parameters areinjected into the last convolutional layer (e.g., the last convolutionallayer 2610 n in FIG. 26) of the convolutional neural network forhandwriting recognition. In some embodiments, the plurality oftemporally-derived parameters and respective weights for the pluralitytemporally-derived parameters are injected into the hidden layer (e.g.,the hidden layer 2614 in FIG. 26) of the convolutional neural networkfor handwriting recognition.

In some embodiments, the device provides (2512) real-time handwritingrecognition for a user's handwriting input using the handwritingrecognition model.

In some embodiments, the device generates (2514) the corpus ofstroke-distribution profiles from a plurality writing samples. In someembodiments, each of the plurality of handwriting samples corresponds(2516) to a character in the output character set and separatelypreserves respective spatial information for each constituent stroke ofthe handwriting sample as it was written. In some embodiments, togenerate the corpus of stroke-distribution profiles, the device performs(2518) the following steps:

For each of the plurality of handwriting samples (2520): the deviceidentifies (2522) constituent strokes in the handwriting sample; foreach of the identified strokes of the handwriting sample, the devicecalculates (2524) a respective occupancy ratio along each of a pluralityof predetermined directions, occupancy ratio being a ratio between aprojected span of said each stroke direction and a maximum projectedspan of said writing sample; for each of the identified strokes of thehandwriting sample, the device also calculates (2526) a respectivesaturation ratio for said each stroke based on a ratio between arespective number of pixels within said each stroke and an overallnumber of pixels within said writing sample. The user device thengenerates (2528) a feature vector for the handwriting sample as thestroke-distribution profile of the writing sample, the feature vectorincluding the respective occupancy ratios and the respective saturationratio of at least N strokes in the handwriting sample, wherein N is apredetermined natural number. In some embodiments, N is less than amaximum stroke count observed in any single writing sample within theplurality of writing samples.

In some embodiments, for each of the plurality of handwriting samples:the device sorts the respective occupancy ratios of the identifiedstrokes in each of the predetermined directions in a descending order;and includes only N top-ranked occupancy ratios and saturation ratios ofwriting sample in the feature vector of the writing sample.

In some embodiments, the plurality of predetermined directions include ahorizontal direction, a vertical direction, a positive 45 degreedirection, and a negative 45 degree direction of the writing sample.

In some embodiments, to provide real-time handwriting recognition for auser's handwriting input using the handwriting recognition model, thedevice receives the user's handwriting input; and in response toreceiving the user's handwriting input, provides a handwritingrecognition output to the user substantially contemporaneously with thereceipt of the handwriting input.

Using the character “

” shown in FIG. 27, an exemplary embodiment is described herein forillustrative purposes. In some embodiments, each input image of ahandwritten character is optionally normalized into a square. The spanof each individual handwritten stroke (e.g., stroke #1, #2, . . . , and#8) is measured when projected onto the horizontal, vertical, the +45degree diagonal, and the −45 degree diagonal of the square. The spans ofeach stroke Si are recorded as xspan(i), yspan(i), cspan(i), anddspan(i), respectively, for the four projection directions. In addition,the maximum spans observed across the entire image is also recorded. Themaximum spans of character are recorded as xspan, yspan, cspan, anddspan, respectively, for the four projection directions. Forillustrative purposes, four directions of projection are optionallyconsidered here, although in principle any arbitrary set of projectionsmay be used in various embodiments. The maximum spans (e.g., denoted asxspan, yspan, cspan, and dspan), and the spans (e.g., denoted asxspan(4), yspan(4), cspan(4), and dspan(4)) of one of the strokes (e.g.,stroke #4) in the character “

” in the four projection directions are shown in FIG. 27.

In some embodiments, once the above spans have been measured for allstrokes 1 through 5, where 5 is the number of individual handwrittenstrokes associated with the input image, the respective occupancy ratioalong each projection direction is computed. For example, the respectiveoccupancy ratio Rx(i) along the x-direction for the stroke S_(i) iscalculated as Rx(i)=xspan (i)/xspan. Similarly, the respective occupancyratios along the other projection directions can be calculated,Ry(i)=yspan (i) lyspan, Rc(i)=cspan (i)/cspan, Rd(i)=dspan (i)/dspan.

In some embodiments, the occupancy ratios of all strokes in eachdirection is sorted separately in decreasing order, and a respectiveranking of all strokes in the input image is thus obtained for eachprojection direction in terms of their occupancy ratios in thatdirection. The ranking of strokes in each projection direction reflectsthe relative importance of each stroke along the associated projectiondirection. This relative importance is irrespective of the order and thedirection by which the stroke has been produced in the writing sample.Thus, this ranking based on occupancy ratios is temporally-derivedinformation that is stroke-order and stroke-direction independent.

In some embodiments, a relative weight is given to each stroke,indicating the importance of the stroke relative to the entirecharacter. In some embodiments, the weight is measured by the ratio ofthe number of pixels in each stroke to the overall number of pixels inthe character. This ratio is referred to as a saturation ratioassociated with each stroke.

In some embodiments, based on the occupancy ratios and saturation ratioof each stroke, a feature vector can be created for each stroke. Foreach character, a set of feature vectors including 5S number of featuresis created. This set of features is referred to as a stroke-distributionprofile of the character.

In some embodiments, only a predetermined number of top-ranked strokesare used in constructing the stroke-distribution profile of eachcharacter. In some embodiments, the predetermined number of strokes is10. Based on the top ten strokes, 50 stroke-derived features can begenerated for each character. In some embodiments, these features areinjected either at the last convolutional layer of a convolutionalneural network, or at the subsequent hidden layer.

In some embodiments, during real-time recognition, an input image of arecognition unit is provided to the handwriting recognition mode thathas been trained with both the spatially-derived features and thetemporally-derived features. The input image is processed through eachlayer of the handwriting recognition model shown in FIG. 26. When theprocessing of the input image reaches the layer (e.g., the lastconvolutional layer or the hidden layer) in which thestroke-distribution profile input is needed, the stroke-distributionprofile of the recognition unit is injected into that layer. Theprocessing of the input image and the stroke-distribution profilecontinues until an output classification (e.g., one or more candidatecharacters) is provided in output layer 2608. In some embodiments, thestroke-distribution profiles of all recognition units are computed, andprovided to the handwriting recognition model as input, together withthe input images of the recognition units. In some embodiments, theinput image of a recognition unit goes through the handwritingrecognition model (without the benefit of the temporally-trainedfeatures) initially. When two or more similar-looking candidatecharacters are identified with close recognition confidence values, thestroke-distribution profiles of the recognition unit is then injectedinto the handwriting recognition model at the layer that has beentrained with the temporally-derived features (e.g., the lastconvolutional layer, or the hidden layer). When the input image and thestroke-distribution profile of the recognition unit passes through thelast layers of the handwriting recognition model, the two or moresimilar-looking candidate characters can be better differentiated due tothe differences in their stroke-distribution profiles. Thus,temporally-derived information related to how the recognition unit isformed by individual handwritten strokes is used to improve recognitionaccuracy, without compromising the stroke-order and stroke-directionindependence of the handwriting recognition system.

The foregoing description, for purpose of explanation, has beendescribed with reference to specific embodiments. However, theillustrative discussions above are not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Many modificationsand variations are possible in view of the above teachings. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, to therebyenable others skilled in the art to best utilize the invention andvarious embodiments with various modifications as are suited to theparticular use contemplated.

What is claimed is:
 1. A non-transitory computer-readable mediacomprising instructions stored thereon, the instructions, when executedby one or more processors, cause the processors to perform operationscomprising: receiving a first handwriting input from a user, the firsthandwriting input comprising a plurality of handwritten strokes, and theplurality of handwritten strokes forming multiple recognition unitsdistributed along a respective writing direction associated with ahandwriting input area of a handwriting input interface; rendering eachof the plurality of handwritten strokes in the handwriting input area asthe handwritten stroke is provided by the user; starting a respectivefading process for each of the multiple recognition units after therecognition unit is completely rendered, wherein during the respectivefading process, the rendering of the recognition unit in the firsthandwriting input are becomes increasingly faded; receiving a secondhandwriting input from the user over a region of the handwriting inputarea occupied by a faded recognition unit of the multiple recognitionunit; and in response to receiving the second handwriting input:rendering the second handwriting input in the handwriting input area;and clearing all faded recognition units from the handwriting inputarea.
 2. The media of claim 1, comprising instructions, which whenexecuted by the one or more processors, cause the processors to performoperations comprising: generating one or more recognition results forthe first handwriting input; displaying the one or more recognitionresults in a candidate display area of the handwriting input interface;and in response to receiving the second handwriting input,automatically, without user selection, entering a top-ranked recognitionresult displayed in the candidate display area into a text input area ofthe handwriting input interface.
 3. The media of claim 1, comprisinginstructions, which when executed by the one or more processors, causethe processors to perform operations comprising: storing an input stackcomprising the first handwriting input and the second handwriting input;generating one or more multi-character recognition results eachcomprising a respective spatial sequence of characters recognized from aconcatenation of the first handwriting input and the second handwritinginput; and displaying the one or more multi-character recognitionresults in a candidate display area of the handwriting input interface,while the rendering of the second handwriting input has replaced therendering of the first handwriting input in the handwriting input area.4. The media of claim 1, wherein the respective fading process for eachrecognition unit is started when a predetermined time period has elapsedafter the recognition unit is completed by the user.
 5. The media ofclaim 1, wherein the respective fading process for each recognition unitis started when the user has started inputting the strokes for a nextrecognition unit after the recognition unit.
 6. The media of claim 1,wherein an end state of the respective fading process for eachrecognition unit is a state with a predetermined minimum visibility forthe recognition unit.
 7. The media of claim 1, wherein an end state ofthe respective fading process for each recognition unit is a state withzero visibility for the recognition unit.
 8. The media of claim 1,comprising instructions, which when executed by the one or moreprocessors, cause the processors to perform operations comprising: aftera last recognition unit in the first handwriting input has become faded,receiving a predetermined revival input from the user; and in responseto receiving the predetermined revival input, reverting the lastrecognition unit from the faded state to an un-faded state.
 9. The mediaof claim 8, wherein the predetermined revival input is an initialcontact detected on a deletion button provided in the handwriting inputinterface.
 10. The media of claim 8, wherein a sustained contactdetected on the deletion button deletes the last recognition unit fromthe handwriting input area and revives the second to last recognitionunit from the faded state to the un-faded state.
 11. A method ofproviding real-time handwriting recognition, comprising: at a devicehaving one or more processors and memory: receiving a first handwritinginput from a user, the first handwriting input comprising a plurality ofhandwritten strokes, and the plurality of handwritten strokes formingmultiple recognition units distributed along a respective writingdirection associated with a handwriting input area of a handwritinginput interface; rendering each of the plurality of handwritten strokesin the handwriting input area as the handwritten stroke is provided bythe user; starting a respective fading process for each of the multiplerecognition units after the recognition unit is completely rendered,wherein during the respective fading process, the rendering of therecognition unit in the first handwriting input are becomes increasinglyfaded; receiving a second handwriting input from the user over a regionof the handwriting input area occupied by a faded recognition unit ofthe multiple recognition unit; and in response to receiving the secondhandwriting input: rendering the second handwriting input in thehandwriting input area; and clearing all faded recognition units fromthe handwriting input area.
 12. A system, comprising: one or moreprocessors; and memory having instructions stored thereon, theinstructions, when executed by the one or more processors, cause theprocessors to perform operations comprising: receiving a firsthandwriting input from a user, the first handwriting input comprising aplurality of handwritten strokes, and the plurality of handwrittenstrokes forming multiple recognition units distributed along arespective writing direction associated with a handwriting input area ofa handwriting input interface; rendering each of the plurality ofhandwritten strokes in the handwriting input area as the handwrittenstroke is provided by the user; starting a respective fading process foreach of the multiple recognition units after the recognition unit iscompletely rendered, wherein during the respective fading process, therendering of the recognition unit in the first handwriting input arebecomes increasingly faded; receiving a second handwriting input fromthe user over a region of the handwriting input area occupied by a fadedrecognition unit of the multiple recognition unit; and in response toreceiving the second handwriting input: rendering the second handwritinginput in the handwriting input area; and clearing all faded recognitionunits from the handwriting input area.